천천히 vs 느리게

Slow your roll. What's the real difference between 천천히 and 느리게? Don't they both mean "slow"? Pull up a chair because I'm taking my time with this one:

천천하다 is the root verb and close to never used. 천천히 is the adjective form and is quite casually used in everyday speech. Examples:

밥 좀 천천히 먹어.
Eat slower, won't you?

천천히 가세요
go slowly

좀 더 천천히 말씀해 주시겠습니까?
Could you speak a little more slowly?

천천히 그리고 꾸준히 하면 이긴다.
Slow and steady wins the race (lit. game)


On the other hand, 느리게 is an adjective whose root verb is 느리다. It also means "slowly" but the difference in nuance is in the action taken. 천천히 is a conscious action that is controllable while 느리게 is out of your control. So, in the last example, if we use 느리게 그리고 꾸준히 하면 이긴다 it doesn't really carry the same feeling as taking your time. Also, saying 밥 좀 느리게 먹어 just sounds unnatural because it's a conscious effort to eat slowly.

However, making an observation on someone else's action is a whole different story. For example:

너 밥 진짜 천천히 먹는 구나
너 밥 진짜 느리게 먹는 구나.
Both could be used to express "Wow, you really eat slowly". Another could be:

Tom은 말을 정말 천천히 해.
Tom은 말을 정말 느리게 해.
"Tom speaks way too slowly" is conveyed but the second example carries more of a negative connotation. Remember, 느리다 is out of your control. Think of an old P4 desktop that takes five minutes to open an email. It's not consciously trying to piss you off; it's just an old computer. Therefore, it might sound like "이 컴퓨터 진짜 느리다!" More examples:

너 지금 일부러 천천히 말하는 거지?
You're speaking slowly on purpose, aren't you?

내 여동생은 설거지하는 게 느리다.
My little sister washes dishes too slowly.

우리는 이해가 꽤 느리다.
We are quite slow on the uptake.

지불이 느리다.
It was slow in making payments.

나는 말이 매우 느리다.
I'm a slow talker.