Here comes another grammatical principle that has no direct translation in English. This one might be my favourite principle of all. (I know, I say that about all of them.)
What it means:
-잖아 (casual) or -잖아요 (high respect) gets added to a word when the speaker is saying something that the listener already knows or should already know.
For example, let’s say your friend asks you how to get from the mall to the movie theatre. You and your friend both know that the mall is at the corner of Davis and Smith street. But you still need to provide that info in order to begin your instructions by telling them that they’ll want to turn left onto Davis when they leave the mall.
In English you might start with, “Okay, so the mall is on the corner of Davis and Smith…” and if your friend is the literal worst, they’ll immediately get offended and be like, “I KNOW the mall is on the corner of Davis and Smith. I’m not stupid!”
But if you had this whole conversation in Korean, you could have added -잖아 to the end of your sentence, indicating that you know your friend already knows where the mall is. Then the misunderstanding would have been avoided.
Another way you can use this grammatical principle is this: Let’s say your brother has been staying up until 3 am every night watching Bangtan Bombs on Youtube, and he’s also waking up at 6 am for work every morning. After a few days, he wonders aloud, “Why am I so tired?” Obviously you’ll reply with “You’ve only been getting three hours of sleep a night!” or “You’ve been staying up all night watching Youtube videos!” If you say these sentences in Korean, you’ll attach -잖아 because your brother knows/should know very well why he’s so tired.
Sort of make sense? We’ll see some examples too. But first…
How to attach it:
-잖아 just attaches to the root of the verb of adjective. Remember that every verb and adjective in Korean ends in 다 and you find the root by removing the 다.
If the verb to which you are attaching -잖아 is in the past or future tense, you’ll conjugate it first and then add -잖아 to the conjugated root.
An interesting thing about this principal is that nothing else ever gets added to the end of it. We know that particles stack on top of each other like crazy in Korean, but if this one is present it’s always the caboose.
늘 똑같은 건 재미없잖아. ~ “It’s no fun being exactly the same all the time.” He’s not delivering any new information here. We all know it’s no fun being exactly the same all the time.
Original verb: 재미없다 – to be boring, to be no fun
그런 날 있잖아 ~ “Those kind of days exist. [and we all know it].”
Original verb: 있다 – to exist, to be found
말 안 해도 느껴지잖아. ~ “Even if you don’t say it, I can feel it. [and you know I can feel it]”
Original verb: 느껴지다 – to be felt
그 호수에 내가 날 버렸잖아. ~ “I threw myself into the lake.” This is not news to the listener. They already knew that 태형 threw himself into the lake.
Original verb: 버리다 – to throw out, to abandon