Il faut – il me faut are from the verb falloir and are used exclusively in the third person form which is impersonal as explained in this previous post. Add a me, te, lui, nous, vous or leur to define WHO is in need:
- Il lui faut un stylo –> He or she (context dependant) needs a pen. The sentence structure is close to: A pen is necessary to him/her (incorrect English).
So, how is this different from Elle a besoin d’un stylo? –> She needs a pen.
Is there a difference between Il lui faut et l a besoin?
The context will mark the difference. In this case, unless a pen is a vital aspect of the context, both sentences are similar: Il lui faut… is slightly more formal, and impersonal (3rd person singular) and does imply that the context, an external factor such an exam, for example, dictates the need for a pen.
Elle a besoin de is often used as a common, even colloquial formulation – this person needs a pen; however, when in doubt, remember that le besoin is Need, neediness and that there are more elegant ways of expressing need. Il lui faut is more natural – elle a besoin d’un stylo likely means the girl doesn’t physically have a pen, therefore someone needs to give her one.
- Il vous faut un sponsor –> You need a sponsor: the situation or context requires you to have a sponsor.
- Tu as besoin d’un sponsor –> You (are in) need (of) a sponsor: this need has been concretely established and focuses on « tu » rather than on the situation itself.
- Tu dois avoir un sponsor (?) –> You must have a sponsor, with uncertainty in meaning: you must have one (but you don’t?) and You must have one (there is no other choice – remove question mark).
Here are examples with a brief note as to what sounds right or not:
- Il me faut partir (my plane takes off in 2 hours) –> I need to leave (it is beyond my control). Can be elegant (or stuffy).
- Je dois partir (I personally need to leave) –> I need to leave (a necessity but it could be my desire to leave or external circumstances)
- J’ai besoin de partir (I have a pressing need to leave) –> This is an unusual construction for usual conversation. Indeed, what kind of need would incite you to leave? On the other hand, if the context is that the mafia is after you, we’d understand.
- Il me faut ce document pour demain* –> I need this document by tomorrow. An impersonal and authoritative request. Clear.
- Je dois avoir ce document pour demain –> I have to have this document by tomorrow. Quite strong and not so agreable as a request. Sounds peevish as a matter of fact.
- J’ai besoin de ce document pour demain –> I need this document by tomorrow. There is some specific need for this document. However, this construction is very common in spoken or informal language.
To express the « pressing urge », or « visceral, physical » nuance loosely associated to the word besoin, let’s introduce the idiom faire ses besoins, which means « to go to the toilet ». We usually use this expression with animals – Le chat a fait ses besoins dans la caisse, Le chien fait ses besoins partout!. A child will moan, J’ai besoin…. to show urgency about using the bathroom. Finally, we speak of besoins fondamentaux, for example in Maslow’s pyramid of needs.
All in all, listen carefully to French speakers and compare: who says what, when and to whom. This will help you determine common expressions using il (me) faut, j’ai besoin de, je dois….
Feel free to write me an email with specific examples and questions.
* soften the request with the conditional: Il me faudrait ce document pour demain, or use the subjunctive: Je voudrais que ce document soit prêt pour demain.