L'Infinitif: Complete Guide to the French Infinitive Form

The infinitif (infinitive) is the most basic form of a verb in French. It is the form you find in the dictionary, and it serves as the foundation for all other verb conjugations. Unlike conjugated verbs, the infinitive does not change to indicate subject, tense, or mood. However, it plays a crucial role in French grammar and appears in countless constructions.

This comprehensive guide will explain everything you need to know about l'infinitif in French: what it is, how to identify the three types, when and how to use it, common constructions, and the mistakes to avoid. By the end, you will be able to use infinitive verbs with confidence and accuracy.

What is the Infinitive?

The infinitive is the base form of a verb. It is the form that you find in the dictionary and the form that appears in verb conjugation tables.

The Three Types of Infinitives in French:

• -ER verbs – Verbs ending in -er (e.g., parler – to speak, manger – to eat, aimer – to like)
• -IR verbs – Verbs ending in -ir (e.g., finir – to finish, choisir – to choose, dormir – to sleep)
• -RE verbs – Verbs ending in -re (e.g., vendre – to sell, attendre – to wait, prendre – to take)

Key Characteristics:

• The infinitive is invariable – it does not change form based on the subject.
• It is often translated into English as "to" + verb (e.g., parler = "to speak").
• It appears in many grammatical constructions, such as after modal verbs, prepositions, and in impersonal expressions.

Example in Context:

• Je veux manger. – I want to eat. (Manger is the infinitive.)
• Il aime nager. – He likes to swim. (Nager is the infinitive.)

Beginner Tip: The infinitive is your starting point for learning any new verb. Learn it well, and you will be able to conjugate it in any tense.

1. The Infinitive After Modal Verbs

One of the most common uses of the infinitive is after modal verbs (verbs that express ability, obligation, desire, etc.).

The Modal Verbs:

• Pouvoir – can / to be able to
• Devoir – must / to have to
• Vouloir – to want
• Savoir – to know how to

Structure:

Subject + conjugated modal verb + infinitive

Examples:

• Je peux parler français. – I can speak French.
• Tu dois étudier. – You must study.
• Il veut partir. – He wants to leave.
• Elle sait nager. – She knows how to swim.
• Nous pouvons venir. – We can come.
• Vous devez finir. – You must finish.

Beginner Tip: Modal verbs are always followed by an infinitive, never by a conjugated verb. Memorize this rule to avoid common mistakes.

2. The Infinitive After Other Verbs

Many other verbs in French are followed directly by an infinitive (without a preposition).

Common Verbs Followed by an Infinitive:

• Aimer – to like (J'aime manger.)
• Détester – to hate (Je déteste étudier.)
• Préférer – to prefer (Je préfère dormir.)
• Adorer – to love (J'adore voyager.)
• Espérer – to hope (J'espère venir.)
• Désirer – to desire (Je désire partir.)
• Aller – to go (Je vais manger.) – Note: Aller + infinitive forms the near future tense.

Examples:

• Elle aime danser. – She likes to dance.
• Nous préférons rester à la maison. – We prefer to stay at home.
• Ils espèrent réussir. – They hope to succeed.
• Je vais acheter une voiture. – I am going to buy a car. (Near future)

Beginner Tip: Some verbs are followed by à or de + infinitive (e.g., commencer à, arrêter de). These must be memorized individually. We'll cover this later.

3. The Infinitive with Prepositions (À and DE)

Many French verbs require a preposition before the infinitive. The two most common prepositions are à and de.

Verbs Followed by À + Infinitive:

• commencer à – to begin to
• continuer à – to continue to
• apprendre à – to learn to
• enseigner à – to teach to
• s'amuser à – to have fun doing
• réussir à – to succeed in
• penser à – to think about (when followed by a verb)
• s'habituer à – to get used to

Examples:

• Je commence à comprendre. – I am beginning to understand.
• Il apprend à nager. – He is learning to swim.
• Elle réussit à finir son travail. – She succeeds in finishing her work.

Verbs Followed by DE + Infinitive:

• arrêter de – to stop doing
• finir de – to finish doing
• oublier de – to forget to
• essayer de – to try to
• décider de – to decide to
• avoir peur de – to be afraid to
• refuser de – to refuse to
• accepter de – to accept to

Examples:

• J'arrête de fumer. – I am stopping smoking.
• Il essaie de comprendre. – He is trying to understand.
• Elle a décidé de partir. – She decided to leave.

Verbs Followed by No Preposition (Directly + Infinitive):

• aimer – to like (J'aime manger.)
• préférer – to prefer (Je préfère dormir.)
• vouloir – to want (Je veux partir.)
• pouvoir – can (Je peux venir.)
• devoir – must (Je dois étudier.)
• savoir – to know how to (Je sais nager.)

Beginner Tip: When you learn a new verb, also learn the preposition that follows it (if any). This is essential for correct usage.

4. The Infinitive with Impersonal Expressions

The infinitive is used after many impersonal expressions (expressions without a specific subject).

Common Impersonal Expressions + Infinitive:

• il est + adjective + infinitive – It is... to...
• il faut + infinitive – It is necessary to... / One must...
• il est important de + infinitive – It is important to...
• il est facile de + infinitive – It is easy to...
• il est difficile de + infinitive – It is difficult to...
• il est impossible de + infinitive – It is impossible to...
• il est interdit de + infinitive – It is forbidden to...

Examples:

• Il est important d'étudier. – It is important to study.
• Il faut partir. – It is necessary to leave. / One must leave.
• Il est facile de comprendre. – It is easy to understand.
• Il est interdit de fumer ici. – It is forbidden to smoke here.

Beginner Tip: Note that il est expressions often require de before the infinitive (e.g., il est facile de). The expression il faut takes the infinitive directly (without de).

5. The Infinitive as a Noun (Nominal Infinitive)

In French, the infinitive can function as a noun. This is called the infinitif substantivé (nominal infinitive). It refers to the act or concept of the verb.

Examples:

• Le manger – eating (the act of eating)
• Le boire – drinking (the act of drinking)
• Le vouloir – wanting / will
• Le pouvoir – power / ability (e.g., le pouvoir du peuple – the power of the people)
• Le savoir – knowledge

Examples in Sentences:

• Le manger est important pour la santé. – Eating is important for health.
• Le vouloir est une force puissante. – Will is a powerful force.

Beginner Tip: This usage is more common in formal or literary French. In everyday conversation, you would use the present participle or a noun instead.

6. The Infinitive After Prepositions (Without a Verb)

The infinitive is used after prepositions like pour, sans, après, avant, etc., when there is no conjugated verb.

Common Prepositions + Infinitive:

• pour + infinitive – in order to / to
• sans + infinitive – without doing
• avant de + infinitive – before doing
• après + infinitive – after doing
• par + infinitive – by doing

Examples:

• Je viens pour parler. – I come to speak. (In order to speak)
• Il est parti sans dire au revoir. – He left without saying goodbye.
• Avant de manger, il faut se laver les mains. – Before eating, you must wash your hands.
• Après avoir dormi, je me suis réveillé. – After sleeping, I woke up. (Après + past infinitive – see section 7)
• En parlant, on comprend mieux. – By speaking, one understands better. (En + present participle – different construction, but related)

Beginner Tip: Use pour + infinitive to express purpose. Use sans + infinitive to express absence of action.

7. The Past Infinitive (Infinitif Passé)

The infinitif passé (past infinitive) is used to express an action that happened before another action. It is formed with the infinitive of avoir or être + past participle.

Structure:

Avoir/Être (infinitive) + past participle

With AVOIR:

• Avoir parlé – to have spoken
• Avoir mangé – to have eaten
• Avoir fini – to have finished

With ÊTRE (reflexive and some movement verbs):

• Être allé – to have gone
• Être sorti – to have gone out
• S'être levé – to have gotten up

Examples:

• Je suis content d'avoir réussi. – I am happy to have succeeded.
• Elle est fatiguée d'avoir travaillé. – She is tired of having worked.
• Après avoir mangé, nous sommes partis. – After having eaten, we left.
• Avant d'être parti, il a fermé la porte. – Before having left, he closed the door. (But note: avant de + infinitive is more common than avant d'être + past participle).

Beginner Tip: The past infinitive is used to emphasize that one action happened before another. It is more common in writing than in everyday speech.

8. The Infinitive in Negative Sentences

When using the infinitive in a negative sentence, the negation surrounds the entire infinitive structure.

Structure:

Ne pas + infinitive

Examples:

• Il a décidé de ne pas venir. – He decided not to come.
• Je préfère ne pas dormir. – I prefer not to sleep.
• Elle m'a dit de ne pas parler. – She told me not to speak.
• Il est important de ne pas fumer ici. – It is important not to smoke here.

Important Rule:

In negative infinitive constructions, ne and pas both come before the infinitive. They do not surround the conjugated verb.

• Correct: Je veux ne pas venir. – I want not to come.
• Incorrect: Je ne veux pas venir. – This is a negative conjugated verb, not a negative infinitive.

Beginner Tip: Remember: in negative infinitive structures, ne and pas both go before the infinitive.

9. Common Mistakes to Avoid

Avoid these frequent errors with the infinitive:

• Using a conjugated verb after a modal verb: ❌ Je peux je parle. → ✅ Je peux parler.
• Using the wrong preposition before the infinitive: ❌ J'arrête à fumer. → ✅ J'arrête de fumer. (Learn which verbs take à and which take de.)
• Forgetting the preposition entirely: ❌ Il essaie comprendre. → ✅ Il essaie de comprendre.
• Placing negation incorrectly in a negative infinitive: ❌ Je préfère pas venir. → ✅ Je préfère ne pas venir.
• Using the infinitive when a conjugated verb is needed: ❌ Il veut que je aller. → ✅ Il veut que j'aille. (Subjunctive is required here.)

10. Practice Exercises

Test your understanding with these exercises.

Exercise 1: Fill in the blanks with the correct preposition (à, de, or nothing) before the infinitive.

1. Je commence ______ comprendre.
2. J'arrête ______ fumer.
3. Je veux ______ partir.
4. Il essaie ______ réussir.
5. J'aime ______ nager.

Answers: 1. à, 2. de, 3. nothing, 4. de, 5. nothing

Exercise 2: Translate these sentences into French.

1. I can speak French.
2. She is learning to drive.
3. It is important to study.
4. I prefer not to go out.
5. After having eaten, we left.

Answers: 1. Je peux parler français. 2. Elle apprend à conduire. 3. Il est important d'étudier. 4. Je préfère ne pas sortir. 5. Après avoir mangé, nous sommes partis.

Exercise 3: Identify the infinitive in each sentence.

1. Je veux dormir.
2. Il a décidé de partir.
3. Nous allons visiter Paris.
4. Il est interdit de fumer.

Answers: 1. dormir, 2. partir, 3. visiter, 4. fumer

11. Memory Tricks and Mnemonics

Here are some simple memory aids to help you remember the rules:

• "Modal verbs go directly with the infinitive – no preposition!" – Always use pouvoir, devoir, vouloir, savoir + infinitive.
• "À for beginners, DE for endings" – commencer à (beginning), arrêter de (stopping). Not a perfect rule, but it helps!
• "Il faut = no preposition" – Il faut is followed directly by the infinitive.
• "Negative infinitive = ne pas together" – Both ne and pas go before the infinitive.

12. How to Practice the Infinitive

Consistent practice is the key to mastering the infinitive. Here are some effective strategies:

• Create flashcards with verb + preposition combinations.
• Write sentences using modal verbs + infinitive.
• Practice converting conjugated verbs to infinitives and vice versa.
• Read French texts and identify all the infinitives you encounter.
• Listen to French podcasts and note how native speakers use the infinitive.

13. Cultural Note: The Infinitive in French Culture

The infinitive is used in many French idioms, instructions, and even in legal texts.

In Instructions and Signs:

Instructions in French often use the infinitive instead of the imperative. This is common in recipes, manuals, and signs.

• Ne pas toucher. – Do not touch.
• Agiter avant utilisation. – Shake before use.
• Mélanger les ingrédients. – Mix the ingredients.

In Legal and Formal Texts:

The infinitive is used in legal language to express general obligations or rules.

• Il est interdit de stationner ici. – Parking is forbidden here.
• Il est obligatoire de porter une ceinture de sécurité. – Wearing a seatbelt is mandatory.

Fun Fact:

In French, the infinitive is often used in dictionaries and verb tables as the headword. It is the form you look up when you want to find a verb.

Final Thoughts

Mastering the infinitive is essential for speaking and writing French correctly. Remember the key points:

• The infinitive is the base form of the verb.
• It is used after modal verbs, other verbs, prepositions, and in impersonal expressions.
• Some verbs require à or de before the infinitive – memorize these.
• The past infinitive expresses actions that happened before another action.
• In negative infinitive structures, ne and pas both come before the infinitive.

With consistent practice, using the infinitive correctly will become second nature. The more you immerse yourself in French, the more intuitive these patterns will become.

Ready to practice? Leave a comment below with three sentences that use the infinitive in different ways (e.g., after a modal verb, after a preposition, in an impersonal expression). We will check your grammar and provide feedback to help you perfect your skills!

Example Sentences:

• Je dois étudier pour réussir l'examen. – I must study to pass the exam.
• Il est important de bien dormir. – It is important to sleep well.
• Après avoir travaillé, je me suis reposé. – After having worked, I rested.

Now it's your turn! Share your sentences below and let us help you master l'infinitif.