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-ian (e.g. Italian); -ite (e.g. Tokyoite)
-er (e.g. performer, etc.); person working with ...
man; person; people
「人」 has other readings with different meanings.
彼女はアメリカ人です。
She is American.
何人来ますかね、今日。
How many people are coming today?
日本人の友達が三人いる。
I have three Japanese friends.