Can They Be Used Interchangeably?
The short answer is no. 'Anything' is an indefinite pronoun that means a thing of any kind.
Note that 'anything' is used more commonly than 'any thing'.
'Any thing' is NOT considered a pronoun. Rather, it is a noun phrase. We use it when we want to:
- emphasize that we are referring to any object not a person or an animal or thoughts and ideas.
This object can fit into
- place another adjective between any and thing.
If you want to put another adjective between 'any' and 'thing', you need 'any thing' as opposed to 'anything'.
- refer to 'things', not 'a thing'.
What about 'Anythings'?
We don't have the word 'anythings', so, if you want to use the plural word 'things', you should say 'any things.'