《牛津》限定词any

1 used with uncountable or plural nouns in negative sentences and questions, after if or whether, and after some verbs such as prevent, ban, forbid, etc. to refer to an amount or a number of something, however large or small

I didn't eat any meat.

Are there any stamps?

He forbids any talking in class.

She asked if we had any questions.

any后接不可数名词或复数名词表示不确切的数或量，这种用法主要用于否定句、疑问句、条件句或表示防止、阻止、禁止等意义的动词后。均为非肯定语境。

2 used with singular countable nouns to refer to one of a number of things or people, when it does not matter which one

Take any book you like.

Any colour will do.

Any teacher will tell you that students learn at different rates.

any还可以表示后接单数名词，表示一些人或事物中的任何一个，而不是表示数量意义。这种用法虽然多见于肯定句，但注意句子多为祈使句，不定式结构，后含有情态动词结构，表示一种可能性，而不是已经确定发生或实际存在的情况。这仍然是非肯定的语境。

例如，He can take any book. 他可以拿任何一本书。但不能说，He took any book. 只能说 He took a book. He took one book.

总之，any既可以表示一些，也可以表示任何一个。都是非肯定语境。认为肯定句中any后只能接单数名词是一种误解。

I can give this book to any student. 一本书不可能同时赠与多个人。非肯定语境。

I gave this book to a student. 肯定语境。

I can give these books to any students. 多本书可以赠与多个人。非肯定语境。

I gave these books to some students. 肯定语境。