잖아

'You know / remember?' shared fact

-잖아 appeals to something the speaker thinks the listener already knows or should admit: 아무것도 안 줬잖아, 아무것도 안 했으니까 'they didn't give you anything, because you didn't do anything.' It can be a reminder, a mild scolding, or a reason offered mid-thought. Every line here is casual and drops the polite 요; adding it gives -잖아요.

Register: casual, no 요