any 后的名词一定是单数还是复数也可以

作为限定词，any既可以表示任何一个人或物（此时后接单数名词），也可以表示大于零的不确定的数或量（此时后接复数或不可数名词）。前者可用于各种句子，但用于肯定句时通常为非肯定语境（例如句子含有表示可能或推测的形容词，不定式表示的未必发生的动作，将来可能发生的动作等。不可用于过去已经确切发生的情景）。后者则通常用于否定句、疑问句和条件句。

具体可参读《韦氏高阶》的释义和例句：

always used before a noun

1 

— used to indicate a person or thing that is not particular or specific

Ask any man you meet, and he will tell you the same thing.

Any one of them could have answered the question.

You can return the product if any defect appears within the first six months.

Any plan (at all) is better than no plan.

Any [=every] child knows that. [=all children know that]

He is as good as any other pitcher in the league.

We can meet any day but Monday.

You could have seen him any afternoon last week.

The recipe uses a large amount of pepper, and not just anypepper, but a special blend imported from India.

You have to be a member to go there. They won't let just any person in.

2 

— used to indicate an amount greater than zero or none — usually used in negative statements, in questions, and in statements with if or whether

You haven't eaten any salad. [=no salad has been eaten]

I can't find any stamps.

Don't pay any attention to him.

There is hardly any difference between the two teams.

They dropped by without any warning.

We don't want there to be any misunderstandings.

The company has denied any [=all] responsibility for the accident.

There are few if any [=few or no] details about the accident.

Do you have any money?

He asked if/whether you had any money.

If there are any errors, report them to me. = Report anyerrors to me.

If you can give me any help, I'd appreciate it. = I'd appreciate any help you can give me.