I've a question regarding the use of 'any'.When to apply an 's' to the noun after the word 'any'?
any reason or any reasons,
any friends or any friend, etc...
"Any" is an adjective. It can mean one out of many, some, or every.
It tells more about the word "reason", but does not have any power over whether a noun is singular or plural.
Any reason you are late?
Are there any reasons why the we can't build that house there?
(not a teacher)