Indefinite form in English. Functions of the infinitive in English. Tense forms of the English infinitive in voices

Infinitive in English is an imfinite form of an English verb that denotes only action, without indicating either person or number. The infinitive answers the questions: what to do? what to do?

To speak - to speak

In Russian, the infinitive is often called indefinite verb form. It is the infinitive that is given in dictionaries as the initial form of the verb.

The formal sign of the infinitive in English is the particle to, which is omitted before the infinitive in some cases.

I was glad to see the car stop.
I was glad to see that the car had stopped.

He must leave before 11 a.m.
He must leave before 11 am.

Infinitive forms

The infinitive in English has four forms in the active voice and two in the passive voice. Forms of the passive voice have only the simple and perfect infinitive of transitive verbs, i.e. verbs used with an object:

Simple infinitive in active voice:

Pauline likes to write letters.
Polina loves to write letters.

Continuous infinitive:

What is Pauline doing? She must be writing a letter.
What is Polina doing? She must be writing a letter.

Perfect infinitive in active voice:

Pauline is glad to have written that letter.
Polina is glad that she wrote this letter.

Perfect continuous infinitive:

Pauline must have been writing that letter since morning.
Polina must have been writing a letter since the morning.

Simple infinitive in passive voice:

This letter seems to be written in pencil.
This letter appears to have been written in pencil.

Perfect infinitive in passive voice:

The forms of the infinitive clearly reflect the relationship with the predicate verb in the sentence.

A simple infinitive in the active and passive voice is used when the action it expresses either occurs simultaneously with the action expressed by the predicate verb in the personal form, or is irrespective of the time of the action:

I am glad to see you.
(simultaneous action)

I'm glad to see you. I like to be given presents.
(action not related to time)

I like it when people give me gifts. To show that an action relates to the future, a simple infinitive is used after modal verbs may, must, should, ought to and after verbs to expect - expect,- intend, to hope- hope to want- want, etc. For example:

You may come tomorrow.
You can come tomorrow.

He must do it immediately.
He must do this immediately.

You should put on a warm hat.
You should wear a warm hat.

I expect to see you next week.
I expect to see you next week.

I intend to go to the seaside this summer.
I intend to go to the sea this summer.

I hope to find him at home.
I hope to find him at home.

Continuous infinitive emphasizes the duration of the action, simultaneous with the predicate verb:

Form perfect continuous infinitive indicates that the action expressed by the infinitive began earlier than the action expressed by the predicate verb and continues to this day:

She seems to have been cooking since morning.
It seems like she's been cooking since the morning.

Perfect infinitive used to denote an action preceding an action expressed by a predicate verb:

I am sorry not to have told you about it earlier.
I'm sorry I didn't tell you about this sooner.

Perfect infinitive after modal verbs must And may expresses the assumption that an action has already taken place:

After modal verbs should, ought to, could, might, was/ were The perfect infinitive denotes an action that should or could have happened, but in fact did not happen.

According to the norms of modern grammar, the English infinitive is one of the three main impersonal ones, along with the participle and the gerund. However, historical evidence suggests that in the Old English period the infinitive had an inflected form, which presumably indicates its origin from a noun. So how do you know what an infinitive actually is? In general, it can be compared with in the Russian language, since, similar to it, the English infinitive simultaneously has the properties of both a verb and a noun. However, it has a number of specific qualities that make life significantly more difficult for people just starting to learn English. To understand what an infinitive is and what it is used with, let’s consider its main functions, forms and the most common examples of use.

Functions of the infinitive

Infinitive form	Pledge
Infinitive form	Active	Passive
Simple	To bite	To be bitten
Perfect	To have bitten	To have been bitten
Continuous	To be biting	-
Perfect Cont.	To have been biting	-

What is the infinitive c to

Particle to is an infinitive, although in itself it does not carry any semantic meaning. The infinitive with to in is always used after:

1. Words the last/first/next:

He is the next to get his passport in our family. - He is the next one to receive a passport in our family.

2. Adjectives expressing some kind of attitude:

We are more than happy to spend this weekend with you. - We will be very happy to spend this weekend with you.

3. Question words:

Can you explain one more time how to fix it? -Can you explain again how to fix it?

4. Constructions verb + noun/place:

I helped my dad to clean the car. - I helped dad wash the car.

5. Constructions for + noun/place:

She waited for the cab to come. - She was waiting for the taxi to arrive.

6. Verbs agree, ask, decide, help, plan, hope, learn, want, would like, promise, refuse, claim, decide and others:

She refused to date her boss. - She refused to meet with her boss.

It should be remembered that with some verbs from this list you can use both a gerund and an infinitive. It all depends on what meaning of the word you want to convey.

"Naked" infinitive

We have looked at what an infinitive with the particle to is, as well as options for its use. Now let's look at the main cases when it can be used without it. So, in English the “naked” infinitive comes after:

1. Modal verbs shall, can, will, may, must/mustn’t, needn’t, could, would, might and should:

I shall bake a cake for his birthday. - I should bake a cake for his birthday.

2. The phrases would rather/sooner, had better, why not, why should (not):

I would rather read a book than watch this film. - I would rather read a book than watch this film.

3. Verbs of sensory or intellectual perception feel, hear, notice, see, watch + addition:

I heard Peter sing a song. - I heard Peter sing.

4. Verbs let/make + object:

Mother let her daughter decide on her own. - The mother allows her daughter to make her own decisions.

Of course, these are not all the linguistic nuances associated with the use of the English infinitive. However, if you understand the basics, further learning a foreign language will go much easier.

In modern English there are three types of non-finite verb forms, and one of them is the Infinitive.

The infinitive in English in its traditional interpretation is the basic dictionary form of the verb (to take - to take, to smile - to smile). We can say with confidence that the infinitive, just like the verb in its personal form, conveys a certain action. But, nevertheless, there is a fundamental difference - in comparison with the verb, the infinitive has neither the category of person, nor the category of number, nor mood.

What is an infinitive in English?

The infinitive in English is one of the types of impersonal forms of the verb (other types include participle ( Participle) and gerund ( Gerund)).

Non-finitive forms of a verb in English often denote an action either as simultaneous or as preceding the one represented by the verb in the finite form.

- I saw them cry in the garden. – I saw them crying in the garden.
(Verb in personal form - saw; infinitive - cry).

— Tom is seen to talk to Rose in a rude manner. – We saw Tom talking to Rose in a rude manner.
(Verb in personal form - seen; infinitive - to talk).

Infinitive forms in English

Let's find out what form of the verb the infinitive is. At the moment, in English there are only six forms of the infinitive: simple, continuous, perfect and perfect continuous. The simple and perfect forms can be in active or passive voice.

Simple
I bought a patch to stop smoking. – I bought a patch to quit smoking.

Continuous
It must be nice to be going to her performances. “It must be great to go to her performances.”

Perfect
I would have gone to university, if I had passed my exam. – I would go to university if I passed the exam.

Perfect continuous
Rachel seems to have been reading my report for an hour already. “It seems like Rachel has been reading my report for an hour.”

Simple passive
Alice could be given a prize for her artwork. – Alice could be awarded a prize for her creativity.

Perfect passive
She claims to have been sacked for her comments. “She claims that she was fired for her statements.”

It is generally accepted that the main questions that Infinitive answers are: “what to do?”, “what to do?”. But it is not always possible to adhere to this form when translating from English into Russian. The above examples are proof of this: reads, read, etc. That is, the infinitive also answers the questions “What is he doing?”, “What will he do?”, “What did he do?” etc.

Using the infinitive in English

The use of the infinitive is determined by several factors, namely: when we want to indicate the purpose of an action; secondly, if we want to give a reason; thirdly, in order to express your opinion. In addition, there are situations where the infinitive is used after certain verbs and adjectives.

Infinitive of purpose quite often used by native speakers, since it is a fairly economical structure. Often the Infinitive of purpose is translated into Russian using complex sentences with the addition of conjunctions and answers the questions: "For what?" "for what purpose?" "for what reason?".

— He bought one hundred tulips to give to his girlfriend. — He bought a hundred tulips to give to his girlfriend.

Sometimes the phrase in order to (so that) or in order not to (so as not to) is used to express the goal:

— In order to score more mark in the examination, she consulted several expert teachers. — To get more marks in the exam, she consulted several expert teachers.
— They never parked the big van in front of the house in order not to upset the neighbors. “They never parked their big van in front of the house so as not to disturb the neighbors.”

Also, the goal infinitive can be expressed using so as to (so that) or so as not to (so that not):

— We set off early so as to avoid the traffic. — We left early to avoid traffic jams.
— Some people need sleeping pills so as to help them to sleep. – Some people need sleeping pills to help them sleep.

The infinitive with the particle to can also indicate the cause of an action or emotional state. The formula is simple: adjective + to-infinitive .

Such adjectives include: disappointed, glad, sad, happy, anxious, pleased, surprised, proud, unhappy, etc.

— We were anxious to get back on the road. “We were afraid to get back on the road.” (We were afraid because we had to get back on the road).

In order to express their point of view, adjectives are often used: difficult, easy, possible, impossible, hard, right, wrong, kind, nice, clever, silly, foolish, etc.

— It is very foolish to take unnecessary risks, like crossing the street without using a crosswalk. - It’s stupid of you to take such risks by crossing the street not at a pedestrian crossing.
Below you can study the table showing the verbs after which we always use the to-infinitive.

Verb (verb)	Usage (example)
Agree (to agree)	Jack agrees to accompany her. Jack agrees to accompany her.
Appear (to appear)	Darkyn didn’t appear to force her to return. Durkin, it turned out, did not force her to return.
Care (to worry)	I will exercise to care to avoid offending anyone. I will learn to pay attention so as not to offend anyone.
Decide (to decide)	When my wife can’t decide what to make for dinner, we order take out. When my wife can't decide what to make for dinner, we order food home.
Demand	He demanded to make an appointment to Mr. Johnson. He needed Make an appointment to Mr Johnson.
Deserve (to deserve)	They deserve to get this prize. They deserve to receive this prize.
Fail (not to succeed)	She failed to involve any volunteers into her project. She was unable to attract volunteers to her project.
Happen (happen)	At last a ship happened to pass that way and Robinson was taken on board. Finally, it happened that the ship turned in his direction, and Robinson was taken on board.
Hope (to hope)	I’ll take you for a ride through more country in a day than you could hope to walk in a week. I'd rather take you on a tour in one day, and you'll see more than you can hope to cover on foot in a week.
Intend (intend)	I don’t intend to let life pass me by. I don't intend to let life leave me.
Learn	I’m going to learn to cook French cuisine. I'm going to learn how to cook French cuisine.
Manage (manage)	How did you manage to keep all that a secret? How did you manage to keep everything a secret?
Offer	Thank you for checking up on me and for the offer to protect me. Thank you for checking on me and offering to protect me.
Plan	How I plan to keep the secret is not your concern. How I plan to keep the secret is none of your concern.
Pretend (pretend)	She wasn’t able to pretend to be okay. She couldn't pretend that everything was fine.
Refuse (refuse)	She thought he would refuse to answer. She thought he would refuse to answer.
Seem (seem)	Felipa didn’t seem to notice anything unusual in his attitude. Felipa did not seem to notice anything unusual in his behavior.
Swear (to swear)	If I release you, you must wear not to tell your master. If I let you go, you must swear not to tell your master.
Wait	There was nothing that couldn’t wait to be discussed at home. There was nothing that needed to wait to be discussed at home.

There are also verbs that can be followed by something like to-infinitive and gerund, but the meaning does not change: can’t bear, can’t stand, cease, continue, hate, like, love, neglect, prefer, propose.

It is quite natural that the question arises: “How to find the infinitive?” The main thing to remember when working with an infinitive is that it is almost always preceded by the particle to. See this article for exceptions.

Detailed description of the infinitive in each form

The infinitive has a category of temporal reference and aspects. The Infinitive of transitive verbs has a voice category - this refers to the morphological category. Let's learn more about this and look at each form separately. And what’s most interesting is that the Infinitive is the only non-finite verb form that has the Continuous form.

Simple Infinitive - simple infinitive (the most necessary form)

The Simple Infinitive is the most used form due to its ease.

Examples of a simple infinitive:

— Martin was excited to see her. – Martin was happy to see her.
— Our company will arrange the transportation of the goods. – Our company will arrange the transportation of goods.

Simple Infinitive Passive - simple infinitive in passive voice

The passive infinitive in English has the same meaning as verbs in the passive voice (Passive Voice).

Method of formation: (to) be + participle (Participle II)

Examples of the simple passive infinitive:

- Nobody wishes to be hated. - Nobody wants to be hated.
— There isn’t much water left to be drained. – There’s not much water left to drain.

Continuous Infinitive - long infinitive

The continuous infinitive expresses an action that is in the process of being performed or lasts for a certain period of time.

Method of formation: (to) be + participle (Participle I)

- You seem to be smiling. - You look like you're smiling.
— This time next week, I’ll be lying on the beach in Croatia. – In a week at this time I will be lying on the beach in Croatia.

Perfect Infinitive Active / Passive - an infinitive denoting a completed action

The Perfect Infinitive is used in the same cases in which it is customary to use all tenses of the Perfect group. It is often used to describe impossible actions in the past tense.

Method of formation (Active): (to) have + participle (Participle II)

— I’m disappointed to have left that town. “I’m disappointed that I left that city.”
— They must have gone the wrong way. “They must have gone in the wrong direction.”

Modal verbs with a perfect infinitive are often used to express the speaker's certainty/uncertainty about past actions.

Must + Perfect Infinitive used when we are confident about something that happened in the past:
— You must have been delighted when you heard you’d won the lottery. – You must have been delighted when you heard that you won the lottery.

Might / may / could + Perfect Infinitive used when we think (but are not sure) that something might have happened in the past:
— The thieves might have escaped by car but we can’t be sure. “The robbers probably left in a car, but we’re not sure.”

Can't + Perfect Infinitive used when we are sure that something did not happen in the past:
— I can’t have left the bag in the supermarket. – I couldn’t leave my bag in the supermarket.

The Passive Perfect Infinitive has the same meaning as simple verbs in Passive Voice.

Method of formation (Passive): (to) have been + participle (Participle II)

— This film could have been directed by Quentin Tarantino. – This film could have been directed by Quentin Tarantino.

Perfect Continuous Infinitive - an infinitive denoting a long-performing action

The perfect infinitive in English can also indicate a continuous action. Perfect Continuous Infinitive denotes an action that is in progress or lasts a certain period of time.

Method of formation: (to) have been + participle (Participle I)

— I’m great to have been living in Barcelona for the last ten years. – I am grateful to have lived in Barcelona for the last ten years.

Infinitive phrases

The infinitive of the verb is also involved in the formation of infinitive phrases, such as complex subject (complex subject), complex object (complex object), the for-to-infinitive construction(turnover with the preposition for).
You can study these topics in more detail by following the links.

Functions of the infinitive in English

Since the verb in its impersonal form answers the question “what to do?”, “What to do?”, accordingly, it cannot serve as a predicate. Since it combines the qualities of a verb and a noun, it is quite obvious that the role of the infinitive in a sentence can be represented as: subject, part of a simple predicate, part of a compound verbal predicate, nominal part of a predicate, definition, complement, circumstance.

Let's look at examples of what part of a sentence an infinitive can be:

— To drink alcohol is harmful. – Drinking alcohol is harmful. (To drink is an infinitive as a subject).

— She didn’t save money for her birthday party. She didn't save money for the birthday party. (Didn’t – save has the function of being part of a simple predicate in combination with an auxiliary verb).

— We had to move to new apartment. – We had to move to a new apartment. (Had to – move has the function of being part of a compound verbal predicate in combination with a modal verb).

— Our plan is to plant as many trees as we can. – Our plan is to plant as many trees as possible. (To plant – has the function of the nominal part of the predicate).

— My classmates invited me to join them in their project. – My classmates invited me to join their project. (To join is an object expressed by an infinitive).

— We are usually the best to sing in the choir. – We are usually recognized as the best when we sing in the choir. (To sing is an infinitive as a modifier).

- I approached him to say hello. - I approached him, to say hello. (To say – has the function of a goal circumstance).

— It is too late to ask him for help. “It’s too late to ask him for help.” (To ask – has the function of circumstance of consequence).

— They will be really excited to see this present. “They will be very excited when they see this gift.” (To see – has the function of circumstance to express an emotional state).

Infinitive in English negation

The rule for a negative infinitive in English is quite simple: we add the negative particle not before the infinitive.

He didn't wait to move a house. – He didn’t wait to move a house.
He was waiting to move to another house. - He expected that won't move to another house.

Exercises on infinitives in English

We suggest you perform a short test. Study the examples below and try to determine which sentences contain an infinitive and which contain a finite verb:

1) Nowadays people eat too much.
2) Nowadays people should eat less.
3) Thomas meets Jane five times a week.
4) Thomas wants to meet his friend today.
5) Argentina lost the match.
6) Argentina is going to lose the match.

Infinitive [?n?f?n?t?v] Infinitive

Infinitive in English - a verb form that expresses action without indicating person, number or mood, and performs the functions of a verb or noun. The infinitive answers the questions: “What to do?”, “What to do?”. Negation is formed by adding the particle not before the infinitive. The infinitive can be used either with or without the particle to.

In English, the infinitive has six forms (four of them in the active voice, and two in the passive voice).
1. Infinitive in the active voice:
A. Simple Infinitive Simple infinitive (Corresponds to the infinitive form of the verb in Russian.)
b. Continuous Infinitive
V. Perfect Infinitive Perfect Infinitive
d. Perfect Continuous Infinitive Perfect Continuous Infinitive
2. Infinitive in the passive voice:
A. Simple Infinitive Passive Simple infinitive passive voice
b. Perfect Infinitive Passive Perfect infinitive passive voice

Infinitive form	Pledge
Infinitive form	Valid	Passive
Simple	to+I	to be + III
Simple	to paint	to be painted
Continuous	to be + IV	---
Continuous	to be painting	---
Perfect	to have + III	to have been + III
Perfect	to have painted	to have been painted
Perfect Continuous	to have been + IV	---
Perfect Continuous	to have been painting	---

The infinitive is used in three syntactic structures:
1. Objective infinitive phrase (alternative name: “Complex object”)
The infinitive is used in most cases in this structure. The objective infinitive phrase looks like this:
Noun/Personal pronoun in the objective case (me, you (singular), him, her, it, us, you (plural), them) + Infinitive
In a sentence:
Subject + Predicate + Object infinitive + Secondary members
She wants him to call her. She wants him to call her.
2. Subjective infinitive phrase (alternative name: “Complex subject”)
Noun/Personal pronoun in the general case + Personal verb as a predicate (usually in the passive voice) + Infinitive
In a sentence:
Subject + Subjective infinitive + Secondary members
Hannah seems to know him. Hannah seems to know him.
3. Infinitive phrase with the preposition for
For + Noun / Pronoun + Infinitive
In a sentence, this phrase can be in different positions, depending on the role it plays.
A. Role of the subject
For him to meet with new people is easy. It is easy for him to meet new people.
b. Role of the complement
She waited for the bus to come. She was waiting for the bus to come.

Using the Simple Infinitive
1. The action indicated by the infinitive and the action expressed by the finite verb or adjective to which the infinitive refers occur simultaneously.
Note: After modal verbs and their equivalents, the action expressed by the infinitive can refer to the future tense.
Michelle was glad to discuss the next meeting with Daniel. Michelle was excited to discuss her next appointment with Daniel.
It may be stuffily in the hall. The room can be stuffy.

2. After verbs such as:
to desire
to expect
to hesitate; hesitate
to intend to intend
to mean intend
to try
to want
to manage succeed
to decide
to fail
to begin
to continue
to arrange
to agree
to prefer
to seem
to ask
to promise
to forget to forget
to demand
to remember
to hate
to like
to hope
to love
and etc.
and also after the expressions:
in order to
so as to
It is astoundingly to remember such long-ago events. It's amazing to remember such long-ago events.
Ian went back home in order to close the windows. Ian returned home to close the windows.
3. After nouns corresponding to verbs.
to decide - decision
to refuse - refusal
to propose - proposal to propose - proposal
to wish - wish
and etc.
His decision to refuse such an offer is foolishly. His decision to refuse such an offer is stupid.
4. After adjectives expressing attitude, encouragement, disapproval, etc.
It was kind of you to accompany me on a journey to New Zealand. It was kind of you to accompany me on my trip to New Zealand.
Michael was pleased to visit some places of his childhood. Michael enjoyed visiting the places of his childhood.

Using the Continuous Infinitive
To denote a continuous action occurring simultaneously with the action expressed by the verbs in the personal form or the adjective to which the infinitive refers. The long infinitive can also be used after modal verbs.
The weather seems to be improving. The weather seems to be improving.

Use of Perfect Infinitive and Perfect Infinitive Passive
1. To denote an action that occurred before another action, expressed by a personal verb or adjective to which the infinitive refers. Very often Perfect Infinitive and Perfect Infinitive Passive are used with verbs:
to acknowledge
to appear
to believe
to consider
to find
to happen
to know
to pretend
to report
to say
to seem
to suppose to believe, to think
to think
to understand
Noah was sorry to have missed the meeting. Noah regretted missing the meeting.
2. To denote an action that will be performed at a certain point in time in the future.
She hopes to have left work until nine o"clock in the evening. She hopes to leave work before nine o'clock in the evening.
3. To express the assumption that the action has already occurred, after the modal verbs may, might, could.
Carter may/might/could have fulfilled everything without us. Perhaps Carter accomplished everything without us.
4. After the modal verb must to denote a logical judgment.
Christian must have been here: there are strange footprints on the floor. Christian must have been here: there are footprints of someone else's shoes on the floor.
5. In negative and interrogative sentences with the verb can to express doubt or surprise.
Can she have gone away without notice? Did she really leave without warning?
6. After modal verbs should, would, could, might, ought to to express an action that could have happened, but did not happen.
He should have ended this talk. He had to end this conversation.
7. To denote an action that was done even though it was undesirable.
He needn't have bought the car on credit. He shouldn't have bought the car on credit.
8. To indicate the probability of what happened, after the modal verbs can and could in negative form: can"t and couldn"t, respectively.
You couldn't have run five kilometer for ten minutes. It cannot be that you ran five kilometers in ten minutes.
9. To denote an action that did not occur contrary to hope, desire or expectation, after verbs:
to expect
to intend to intend
to hope
to mean
and after the expression would like (I would like)
I intended to have warned him, but I forgot. I intended to warn him, but I forgot.

Using the Perfect Continuous Infinitive
To denote a continuous action that began before the action expressed by the finite verb or adjective to which the infinitive refers.
Leah is known to have been working in this firm for six years. It is known that Lea has been working in this company for six years.

Using the infinitive without the particle to
1. After auxiliary and modal verbs, except ought (to), to have (to), to be (to).
He must come back immediately. He must return immediately.
Brandon is to come at six o"clock in the morning. Brandon must come at six o'clock in the morning.
2. After verbs perceptions in the active voice.
Andrew saw her looking out of the window. Andrew saw her looking out the window.
(Other verbs of feeling and perception are in the material " ".)
3. After the verbs to let, to make, to have, all three mean “to receive”, as well as to know in the meaning of “to know” in the active voice.
Don't let him abuse you. Don't let him abuse you.
4. After expressions:
had better it would have been better
would rather be better
cannot but cannot help
nothing but nothing but
I would rather buy a sport bike. I'd rather buy a sports bike.
5. In interrogative sentences that begin with the words why not (why not).
Why not go walking? Why don't we take a walk?
6. After the verb help (help), the infinitive can be used with or without the particle to. But in the passive voice and in negative sentences, the particle to is always used after help.
James will help you (to) carry the traveling bag. James will help her carry her travel bag.
She was helped to carry the traveling bag. They helped her carry her travel bag.
7. The particle to is usually not used before the second infinitive when they are connected using conjunctions:
and and
except
but but
or or
than
What would you choose: to buy a good car or visit Switzerland? What would you choose: buy a nice car or go to Switzerland?
8. The particle to is not used if it is clear from the context what is being discussed.
Note: If the verb to be is used, then the particle to cannot be omitted.
- Let's play a game of poker! Let's play a game of poker!
- I don't want (to). I don't want.
9. After the verb to like, the infinitive phrase is omitted along with the particle to.
Caleb can buy everything he likes. Caleb can buy whatever he wants.
10. If the infinitive phrase plays the role of a subject or definition and has its own subject, then the preposition for is used before the subject of the infinitive phrase.
He bought a gas sprayer for her to be on the defensive. He bought her a pepper spray so she could defend herself.

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In English infinitive(Infinitive) is a word that denotes an action, but does not indicate a person or number. In Russian, the English infinitive corresponds to the infinitive form of the verb, which answers the questions “what to do? what to do?": to live - to live.

The formal sign of the infinitive is the particle to:

to write- write, to read- read, to drink- drink, to think- think.

If there is a particle before the verb to, then before you is an infinitive (or an indefinite form of a verb). Sometimes the infinitive can be used without a particle to.

The negative form is formed using a particle not, which comes before the infinitive: not to use - do not use.

It is difficult to use .- Difficult use.
It is difficult not to use .- Difficult do not use.

Infinitive forms

In English, the infinitive has 6 forms (unlike Russian, which has only one form). To understand well the meanings of the infinitive forms, you need to have an understanding of the verb.

Simple infinitive. Indefinite Infinitive

Infinitive in the form Indefinite (Simple) or simple infinitive is the basic form and represents the verb in the dictionary (for convenience, the particle in the dictionary to often omitted). This form of the infinitive is in the same tense as the verb that precedes it.

I was glad to see her. — I was glad to see her (simple infinitive in the active voice).
The child didn't like to be washed. — The child did not like being washed (simple infinitive in the passive voice).

Compare the use of the simple infinitive in the active and passive voice: to help - to be helped
I am glad to help you. - I am glad to help. (I'm glad I'm helping).
I am glad to be helped. - I'm glad they're helping me.

Perfect infinitive. Perfect Infinitive

Infinitive in the form Perfect or perfect infinitive denotes an action that precedes the action of the predicate verb.

I was very glad to have met you. - I am very glad that I met you (perfect infinitive in the active voice).
Sorry not to have noticed you. - Sorry that I didn’t notice you (perfect infinitive in the active voice).
The child was happy to have been brought to the circus. — The child was happy that he was brought to the circus (perfect infinitive in the passive voice).

Compare the use of the Simple Infinitive and the Perfect Infinitive in the active voice: to see - to have seen
I am glad to see you. - Glad to see you. (Glad to see you.)
I am glad to have seen you. - Glad I saw you.

Long infinitive. Continuous Infinitive

Infinitive in the form Continuous or long infinitive emphasizes the duration of an action occurring simultaneously with the action of the predicate verb. This form is used only in the active voice.

He doesn't seem to be writing something. — It seems he is writing something now (long infinitive in the active voice).

Perfectly continuous infinitive. Perfect Continuous Infinitive

Infinitive in the form Perfect Continuous or perfect continuous infinitive emphasizes that the action began earlier than the action of the predicate verb, lasted for a period of time and is still lasting. This form is also not used in the passive voice.

He didn't seem to have been writing all day. “It seemed like he was writing all day.”

Infinitive forms in the table

The meaning of different forms of the infinitive in the table
Infinitive forms	What am I happy about?
Simple	I am glad to speak to you.	Glad to talk to you. (I always rejoice when I talk to you).
Continuous	I am glad to be speaking to you.	I'm glad I'm talking to you now.
Perfect	I am glad to have spoken to you.	Glad I talked to you.
Perfect Continuous	I am glad to have been speaking to you.	I’m glad that I’ve been talking to you for a long time (all this time).
Simple Passive	I am (always) glad to be told the news.	I'm always glad when people tell me news.
Perfect Passive	I am glad to have been told the news.	Glad you told me the news.

Using the infinitive without the particle to

Most often the infinitive in English is used with the particle to, but there are cases when the particle to not used before an infinitive.

The infinitive is used without particle to in the following cases:

After can, could, must, may, might, will, shall, should, would And need (in the modal sense). Exceptions are modal verbs have to, ought to, be to.

IN complex addition after sensory verbs feel(feel), hear(hear), see(see), watch(observe), notice(notice):
I saw him leave the office. — I saw him leave the office.
I heard him go down the stairs. “I heard him come down the stairs.
But: if the listed verbs feel, see, hear, watch, notice are used in the passive voice, then the particle precedes the infinitive to:
He was seen to leave the office. — We saw him leave the office.
In a complex object after verbs make(meaning “to force, compel”) And let(meaning “to allow, allow”). Again, if these verbs are in the passive voice, then the infinitive is used with the particle to.
I can't make you take this medicine. “I can’t force you to take this medicine.”
We let her go to the party. — We allowed her to go to the party.
She was made to rewrite the test. — She was forced to rewrite the test (was made - passive verb).
After the verb help(to help) the infinitive can also be used with a particle to, and without it. Both options are acceptable, with the option without to less formal.