When we talk about the infinitive, we are referring to the part of the verb that is the equivalent of the English ‘to do…’, for example the French infinitive avoir means ‘to have’, parler means ‘to speak’ and so on. If you wish to look a verb up in the dictionary, the infinitive is the form you must look for.
The most common use of the infinitive is as the second verb, coming straight after a finite verb (a verb which has a subject). Here are a few examples:
Je veux aller en ville. – I want to go to town.
Tu as fait marcher la machine? – Did you make the machine work?
Il faudra quitter demain. – It will be necessary to leave tomorrow.
Nous allons louer un appartement qui donne sur la mer. – We’re going to rent a flat that overlooks the sea.
Est-ce que vous pourriez acheter des fruits? – Could you buy some fruit? (Notice there is no ‘to’ following could in the English translation.)
Elles voulaient sortir avec nous. – They wanted to go out with us.
In the above examples, the infinitive follows the first verb directly, but in many cases the finite verb must be followed by the prepositions a (with a grave accent) or de before the infinitive.
Examples where preposition à is needed:
Je les aide à faire les devoirs. – I help them to do their homework.
Tu t’attends à recevoir beaucoup de cadeaux? – Are you expecting to receive lots of presents?
Il m’invite à jouer au tennis. – He invited me to play tennis.
Nous nous sommes mis à rire. – We started to laugh.
Vous vous êtes decidé à sortir? – Have you decided to go out?
Elles reussissent à suivre un regime. – They’re managing to (succeeding in) following a diet.
Examples where preposition de is needed:
J’ai besoin de prendre un jour de congé. – I need to take a day off.
Tu as envie d’aller chez eux? – Do you want to go to their house?
Elle a cessé de leur rendre visite. – She has stopped visiting them.
Nous avons decidé de partir en Espagne. – We’ve decided to go to Spain.
Vous nous avez dit de nous arrêter. – You told us to stop.
Ils leur ont demandé de quitter. – They asked them to leave.
These are just a few examples as the full lists are too long to be included here, but a dictionary will of course give this information.
In the case of finite verbs, when using the negative, we put ne in front of the verb and pas (or jamais/rien/personne/plus/aucun/nul/point etc.) after it. However, with the infinitive, the two parts of the negative both precede the infinitive, as in these examples:
Je suis arrivé à ne pas depenser beaucoup. – I managed not to spend much.
Tu as decidé de ne plus lui parler? – Have you decided not to speak to him any more?
Elle continue à ne pas manger de viande. – She’s continuing not to eat meat.
Nous avons peur de ne pas savoir nous faire comprendre. – We’re afraid of not being able (knowing how) to make ourselves understood. (Notice that this sentence contains a string of three infinitives: savoir, faire and comprendre.)
Vous apprenez à ne jamais vous fâcher. – You’re learning never to get angry.
Ils commencent à ne plus vouloir jouer au football. – They’re starting not to want to play football any more.
The infinitive is sometimes used instead of the vous (polite or plural) form of the imperative, in recipes or public notices for example:
Laisser cuire pendant deux heures. (Let it) cook for two hours.
As well as the present infinitive, there is a perfect infinitive meaning ‘to have done…’ If the verb forms the perfect tense with avoir, the perfect infinitive will be formed with avoir plus the past participle of the verb. If the verb forms the perfect tense with etre, then etre will be used with the past participle to form the perfect infinitive:
avoir fait – to have done, to have made
avoir fini – to have finished
avoir vendu – to have sold
être parti – to have left
être descendu – to have gone down, to have got off (transport)
s’être endormi – to have fallen asleep.
Here are some examples of how the perfect infinitive is used in sentences, often after prepositions:
Apres avoir fait le ménage, elle s’est reposée. – After doing the housework, she had a rest.
Sans avoir vendu sa maison, elle a acheté un appartement. – Without having sold her house, she bought a flat.
The infinitive is not a complicated aspect of French grammar. Perhaps the trickiest thing is learning when to use the prepositions à or de after the preceding verb. This may take time, but will be easier the more you practise speaking and listening.