Modalverben: pouvoir, vouloir, devoir

Three verbs do the work of English "can", "want" and "must": pouvoir, vouloir and devoir. Unlike English modals, they are full verbs with a complete set of endings, and all three are irregular.

The pattern is the same for all three: the singular and the ils form share a changed stem (peu-, veu-, doi-), while nous and vous keep the infinitive stem.

Modal + infinitive

The modal is conjugated and the next verb stays in the infinitive, as in English but with no "to": Je peux parler français. - I can speak French. Tu veux venir au marché ? - Do you want to come to the market? On doit partir à six heures. - We have to leave at six. English speakers sometimes add a preposition, *Je veux de venir; there is none.

In the negative, ne... pas goes around the modal: Je ne peux pas venir ce soir.

can: pouvoir or savoir?

English "can" covers two French verbs. Pouvoir is about being able or allowed: Je peux venir demain. Savoir is about a skill you have learned: Je sais nager. - I can swim. Elle sait jouer du piano.

Polite requests

Je veux sounds blunt in a shop or café. Use the conditional forms: Je voudrais un croissant, s'il vous plaît. - I'd like a croissant. Vous pourriez m'aider ? - Could you help me?