This post focuses on falloir but I suggest you keep this verb as part of the triumvirate “devoir-pouvoir-falloir”. Comparisons will help you capture differences in meaning.
For starters:
Vous pouvez prendre des vacances mais vous devez demander la permission à votre supérieur. Dans cette entreprise, il faut toujours remplir le formulaire de demande de vacances.
In short…you have permission, you are allowed to take holidays but you must ask your supervisor first. In this company, we always need to fill out the Holiday request form.
To master falloir, first remember that it can only be used in an impersonal IL form:
- Il faut remplir le formulaire.
When a verb follows falloir, always use the infinitive (a verb’s dictionary form).
- Il faut lire pour améliorer son vocabulaire.
Sure, but…. what does it mean??
“Falloir” refers to general needs, requirements or a necessity.
- Il faut boire pour vivre. We must/need to drink to stay alive.
- Il faut gagner de l’argent dans notre société moderne. It is important/necessary to earn money in our modern society.
- Il faut faire écrire plusieurs brouillons avant d’aboutir à la version finale. One needs to/You have to write several drafts before ending up with the final version.
It’s also an impersonal way to give orders:
- Il faut éteindre le natel (Swiss word for “portable, téléphone cellulaire”) en réunion. (Turning off cell phones during a meeting is assimilated to a general necessity.)