A" IS USED FOR AN ELEMENT THAT IS NOT SPECIFIC "AN" FOR A SPECIFIC ELEMENT
SOME/ANY
I need to buy some books
They didn't learn any new word in class
some (some or some of) in affirmative sentences and when you want to ask or offer something. it is
used with both countable and uncountable nouns. On the other hand, any is used in questions (some,
some of) or in negative sentences (none, nothing of). Note that any is used for uncountable and
countable plural nouns
MUCH/MANY
I don't drink much coffee
They have many friends in Germany
"Much" is used when we are talking about a singular noun. It is used for things that you cannot count, that is, for countless
things. "Many" is used when we are talking about a plural noun. Used for things you can count