types of modals

[hela]

Dear teachers,

Would you please tell me what is :

a) deontic modality,
b) epistemic modality ?

Thanks a lot,
Hela

[Tdol]

Epstemic modality-the speaker's attitude towards the truth of the statement- he can' have finished already.
Deontic modality- the speaker's affecting events- You may go home when you have finished.