Where is the difference between -ТО, -НИБУДЬ, -ЛИБО, КОЕ-

Кто-то зашёл в магазин. Someone entered the store. 
Кто-нибудь хочет есть? Is anybody hungry?
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Мы кое с кем должны встретиться.  We should meet someone.

Cases in which they are necessary to use:
1.
–ТО: When you do not know or remember who, what or where it was.
Example: Я где-то тебя уже видела. I have already seen you somewhere. (But I do not know exacty where. Or I do not remember where.)
2.
–НИБУДЬ: When it is not important who, what or where.
Example: Дай мне что-нибудь поесть. Give me something to eat (I do not care what you give.)
- ЛИБО: it is a synonym for "-нибудь" and it is used in official situation. 
3.
КОЕ-: When you do not want to tell who, what and where. Or you do not want to say it now but will tell later. 
Example: Я кое-что тебе должен вернуть. I have to return something to you. (I know what it is but now I do not want to say it or do not have time to tell about it) 

 


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