Capacité, possibilité, obligation, interdiction

Fiche

1. Can / be able to

• Can permet d'exprimer la capacité ou la possibilité. Can't, au contraire, exprime l'incapacité ou l'impossibilité.

• Au présent : can est invariable et toujours suivi de la base verbale.
I can play tennis but I can't surf. Can you teach me?

• On peut utiliser également be able to. Il faut conjuguer be correctement !
I am able to play tennis but I'm not able to surf.

• Au passé : can / can't → could / couldn't ; be able to → was / wasn't / were / weren't able to.
I could play tennis when I was young but I couldn't surf.
I was able to play tennis but I wasn't able to surf.

• Au futur : on utilise will be able to .
I will be able to play tennis but I won't be able to surf.

2. Must / have to

• Must permet d'exprimer l'obligation. Mustn't, au contraire, exprime l'interdiction. Ils n'existent qu'au présent.

• Au présent : must est invariable et toujours suivi de la base verbale. Il sert à exprimer des règles, des lois valables pour tout le monde.
We must cross the road at the zebra crossing. You mustn't drive over 50 km/h here.

• Have to permet d'exprimer une obligation ponctuelle ou personnelle.
You have to turn right to get to the cinema.

• Don't have to exprime une absence d'obligation.
You don't have to play with her if you don't want to.

• Au prétérit : must → had to.
I had to stop at the traffic lights!

• Au futur : must → will have to.
I will have to stop at the traffic lights.

Le sais-tu ?

Attention !

Can ne s'emploie pas au futur !