没 + Verb/Noun
The adverb 没 (méi) is used for negation, meaning "not" or "have not." In the expression 没什么, it combines with 什么 to mean "it's nothing" or "there's nothing," commonly used to downplay something.
今天我没吃早饭就出门了。
jīntiān wǒ méi chī zǎofàn jiù chūmén le.
I left the house today without eating breakfast.
她还没回来,你再等一下吧。
tā hái méi huílái, nǐ zài děng yīxià ba.
She hasn't come back yet — please wait a little longer.
没关系,我不介意。
méi guānxi, wǒ bù jièyì.
It's okay, I don't mind.