Thread: " Мысль гуляла вольной птицей по лицу " (cases)

Originally Posted by rouloubole

-ся always means passive ?

Unfortunately, no.

The main function of -ся/-сь is reflexiveness:
Он моет пол. — “He is washing the floor.” (non-reflexive)
Он моется. — literally, “He is washing himself.” (reflexive)

It also can be used for passive:
Пол моется каждый день. — “The floor is washed every day.”

With some other words, it also mean reciprocal:
Они целуются. — They are kissing each other.

With some words it is used for no evident reason:
Эта собака не кусается. — “That dog doesn’t bite”.

Some words are just not used without -ся:
Он смеётся. — “He is laughing.”
Он боится. — “He is afraid.”