-잖아요

as you know, you might recall

Explanation

This expression is used when the speaker wants to state a reason that the listener should also be aware of or when the speaker wants to remind the listener of a reason that he or she has apparently forgotten.

It is used only in conversation and not in written Korean.

Also, it is not used in formal speaking situations.

Details

Kimchi Reader

Indicates that the speaker is reminding the listener of a reason they should be aware or might have forgotten.