Expired question
Ataf Alsam's Tu Janne Na

Can someone please explain the grammar of the phrase "tu janne na"? I understand it means "you don't know", but the grammar for the phrase is different from what I have seen before. 1) it appears to be in past tense -- why is that so? 2) given that "tu" is the most informal way to address someone, why is the conjugation "janne" instead of "janna" or "janni"? I would have probably said this sentence as "tu nehin jannti" (speaking to a female), but it wasn't structured this way. Why not?