Phải (V 1)

Situations

S1: My hasn't finished her homework but wants to watch TV. Her mother says:

Con phải học bài trước khi xem ti vi.
(You must finish your homework before watching TV.)

Phải is used here to give a command or a request.

S2: Nam declines an invitation to go to Đà Lạt.

Cám ơn, tôi không đi vì tôi phải học thi.
(Thank you, I can't go because I have to study for exams.)

Phải is used to express compulsion, obligation, or necessity.

Definition

Phải, as a verb, is used to give a command or request, or to express what must be done as a compulsion or obligation.

Related Expressions

• phải, nên, cần: These verbs express requirement, compulsion, or necessity. Phải is a stronger command than nên.

[1a] Anh phải đi ngủ sớm. (You must go to bed early.)
[1b] Anh nên đi ngủ sớm. (You should go to bed early.)

When speaking about a necessity, we use phải instead of nên.

[2] Tôi phải / *nên đi ngủ sớm (để sáng mai dậy đúng giờ).
    (I have to go to bed early.)