Modal verbs

We use MUST/HAVE TO to express obligation.

e.g. I must help with chores. (It's my duty. I'm saying so)

Aš privalau padėti atlikti namų ruošos darbus.

e.g. I have to tidy my room. (It's my duty. My parents told me)

Aš turiu susitvarkyti savo kambarį.

We use MUSTN'T to express prohibition.

e.g. We mustn't talk in class.

Mums draudžiama kalbėtis klasėje. (It's against the rules)

We use DON'T HAVE TO to express lack of obligation.

e.g. We don't have to wear a uniform at school. (It isn't necessary)