1(after a verb or adjective) one who (is) ...
2(after a noun) person involved in ...
3-er
4-ist
5(old) (used at the end of a command)
6(old) this
7(used after a number or 後|后 or 前 to refer to sth mentioned previously)
8(used after a term, to mark a pause before defining the term)
Examples
wǒ我shì是gāi该duì队de的lǐng dǎo领导zhě者。
我是该队的领导者。
I am the leader of this team.
我是最快的跑者。
I am the fastest runner.
许多工作者饿死了。
Many workers starved to death.