pants

[English4everyone]

When we want to ask about pants, trousers, glasses, scissors, etc., should we say:
What are these? or What is this?

[5jj]

If you need to ask, you'll probably say 'what is this?'.

[English4everyone]

So you mean we say what's this? and the answer is they are pants, glasses, scissors, etc.
Is it correct in English grammar?

[5jj]

So you mean we say what's this? and the answer is they are pants, glasses, scissors, etc.
Is it correct in English grammar?

It's a question of communication, not grammar. The person asking the question has no idea that the singular object is denoted by a plural noun in English, hence the "What's this?". The person reponding might well say, "It's a pair of pants", but they might just say, "They're pants".