The infinitive is the form of the verb with no person or tense marked. It names the action, the state, the event or the change without saying who acts or when. It is found in dictionaries and in the basic structures of the French verbal system. In a sentence, it often serves as the starting form before conjugation, such as to speak, to finish, to take, to be or to go.

Model of regular -er infinitives

Idea
The infinitive in er is the most common form for many everyday verbs.
The infinitive in er keeps a very stable base across the entire verb family.
The infinitive in er often serves as a starting point to create other verb forms.

The great family of -er verbs follows the most regular and most common pattern in French. Their infinitive ends with -er and the stem remains generally stable, as in to speak, to eat, to begin, to love or to watch. Some verbs change slightly in writing to preserve the pronunciation, like to eat and to begin, but they always belong to the same model. This group serves as the base for a very large number of everyday verbs.

Model of regular -ir infinitives

Idea
The infinitive in ir appears in a very useful regular family for actions that change.
The infinitive in ir helps to recognize verbs like choisir and grandir.
The infinitive in ir stays without person or tense, even when the verb seems to move a lot.

Regular -ir verbs form another productive family. Their infinitive ends with -ir and many common verbs follow this pattern, such as to finish, to choose, to grow, to succeed and to reflect. Their form is easily recognizable, even if their conjugation behavior belongs to a model that is different from -er verbs. To identify them, look at the infinitive and compare it with the basic conjugated forms.

Model of frequent -re infinitives

Idea
The infinitive in re often marks less regular but very frequent verbs.
The infinitive in re often requires more attention because its family varies more.
The infinitive in re remains a useful base form to understand many common verbs.

The -re verbs form a less regular but very useful family in everyday language. The infinitive ends with -re, as in to take, to sell, to put, to wait or to lose. Many of these verbs change more when conjugated, but their infinitive remains the starting point for recognizing them. This group contains several essential verbs for speaking and writing with accuracy.

Very frequent irregular infinitives

Idea
Certain infinitives are very irregular and must be memorized as they are.
Certain essential verbs like avoir and aller do not follow a simple regular pattern.
The verbs faire, pouvoir and vouloir are common infinitives to know very quickly.

Some very frequent infinitives do not follow the major regular patterns. The most important at the start are to be, to have, to go, to do, to be able to and to want. They appear everywhere in the language, including in Constructions verbales, Verbes modaux and Futur proche. Their form must be recognized immediately, as they serve as the base for many constructions.

Infinitive after another verb

Usage	Explanation
Intention	We use the infinitive after a verb to say what we want to do.
Capacity	We use the infinitive after a verb to talk about an action we know how to do.
Upcoming action	We use the infinitive after a verb to announce an action that is coming.

After certain verbs, an infinitive is used directly. The pattern is verb + infinitive, as in I want to leave, she knows how to swim, we can enter or they like to read. This structure is used to express intention, ability, plan, preference or permission. Verbs like to want, to be able to, to must, to know and to like are very common in this type of construction, which also prefigures forms studied in Constructions verbales and Verbes modaux.

Infinitive after a preposition

Usage	Explanation
Avant de	We use the infinitive after a preposition to link one action to another, for example with avant de.
Sans	We use the infinitive after a preposition to say that an action is done apart, for example with sans.
Pour	We use the infinitive after a preposition to express a purpose, for example with pour.

The infinitive often follows a preposition to form a fixed expression. You mainly encounter before doing + infinitive, without + infinitive, for + infinitive, to + infinitive and of + infinitive. We say before leaving, without speaking, to succeed, to do or to come depending on the construction. The preposition is part of the expression and does not disappear. In these groups, the infinitive keeps its base form and completes the meaning of the sentence.

Infinitive used as a noun

Usage	Explanation
General action	We use the infinitive as a noun to talk about an action in general, without specifying who does it.
Abstract idea	We use the infinitive as a noun to name an idea or a habit.
Pleasure noun	We use the infinitive as a noun when the action itself becomes the fun subject of the sentence.

The infinitive can serve as a noun to speak of an action in general. In this case, it designates the activity itself, like to drink, to read or to live. It can also appear with a determiner in expressions like the living together or the drinking and the eating depending on the context. This use allows treating the action as an idea, a habit or a topic of discussion, without conjugating it.

Formation of the past infinitive

Idea
The past infinitive is formed with avoir or être and a past participle.
The past infinitive is used to show that an action is anterior to another.
The past infinitive keeps the idea of a completed action, even without a specific subject.

The past infinitive is formed with to have or to be + past participle. We use to have for most verbs, as in to have spoken, to have finished, to have taken. We use to be with verbs that form with to be in compound tenses, such as to have gone, to have come, to have fallen. This form expresses an action completed before another action. It often appears after a preposition or in a broader verbal construction.

Very frequent verbal constructions

Usage	Explanation
Obligation	We use devoir + infinitive to express a necessity or rule.
Futur proche	We use aller + infinitive to announce a very near action.
Passé récent	We use venir de + infinitive to say that an action happened just a moment ago.

Several very frequent verbal constructions rely on the infinitive. To must + infinitive expresses obligation or probability, as you must leave. Go + infinitive is used for the Futur proche, as in we are going to go out. Come to + infinitive indicates a very recent action, as she has just arrived. These structures are directly linked to the functioning of the infinitive and recur constantly in everyday language.