What's so funny? The difference between these two little jokers is no laughing matter.
농담 (弄談)
kidding, joking (through speech)
장난
playing, teasing (through action)
The English explanation sounds a bit off but stay with me. 농담 is easy to define because it has the 말씀 담 (談) in it's name. You know off the bat that it's something to do with speaking. The preceding character is 희롱 농 (弄) which is like a taunt, mock or jeer. You may have seen this in 성희롱 (性戱弄) which means "sexual harassment".
장난 is a bit different. This natively Korean expression is more encompassing. It can be an action speech or a sticked out tongue (메롱) given to some kid onthe subway giving you the stink eye. Whatever it is, it's a joke. You can also see this in 장난감 which is a "toy" or also my personal favorite but not so common 붓장난 which can be interpreted as "hack writing". The idea is that someone's writing is so bad that it must be a joke.
Examples:
장난 아냐! 사실이야.
I'm not kidding! I'm telling the truth.
어렸을때 그 곰 인형은 제일 좋아하는 장난감이었어요.
That teddy bear was my favorite plaything as a kid.
그것도 농담이라고 해요?
You call that a joke?
농담할 기분이 아니에요.
I'm not in the mood for jokes.
이제 농담은 그만 해야겠군요.
I seems I should stop joking now, yeah?
농담은 집어치우고 진짜 이유를 말해 봐요.
All joking aside, what's the real story?
