A1
Asking a yes/no question
The two ways Cantonese asks a yes/no question — the A-not-A form built with 唔, and the sentence particle 呀 — and why 嗎 marks a sentence as translated from Mandarin.
The A-not-A form
Say the verb, negate it with 唔, and let the listener pick. This is the standard way to ask in Cantonese and you will hear it constantly.
你去唔去？
Nei5 heoi3 m4 heoi3?
Are you going?
你係唔係學生？
Nei5 hai6 m4 hai6 hok6saang1?
Are you a student?
今日凍唔凍？
Gam1jat6 dung3 m4 dung3?
Is it cold today?
Two-syllable verbs shorten the first half — 鍾唔鍾意, 得唔得閒 — exactly as Mandarin does.
呀 at the end
A statement with 呀 on it becomes a question, and a softer one. 呀 is the everyday particle and it does far more work in Cantonese than 吗 does in Mandarin.
你係學生呀？
Nei5 hai6 hok6saang1 aa4?
You’re a student?
你食咗飯未呀？
Nei5 sik6zo2 faan6 mei6 aa3?
Have you eaten?
The tone on 呀 changes what it does — rising for a question, falling for a soft statement — which is why romanisations write it differently in different places.
Not 嗎
嗎 exists, in written Chinese and in Cantonese read aloud from a page. It is not what anyone says.
你係學生嗎？
你係學生呀？
嗎 is the single clearest sign of a sentence translated out of Mandarin rather than spoken. 呀 or the A-not-A form is what a Cantonese speaker reaches for.
咩 for surprise
咩 asks a question you are not expecting to be true — the really? of Cantonese.
真係咩？
Zan1hai6 me1?
Really?
你唔知咩？
Nei5 m4 zi1 me1?
You mean you didn’t know?
Answering
No word for yes. Repeat the verb, or negate it.
——你去唔去？——去。
— Nei5 heoi3 m4 heoi3? — Heoi3.
— Are you going? — I am.
係呀 and 唔係 are the general-purpose confirm and deny, and 冇錯 (not wrong) is a common way to agree.