If I want to ask for the definition of a countable noun(e.g. cat). Should I say

  • “What is a cat?"


  • “What are cats?”

Are there any difference between the two expressions?


1 Answer 1


Either can be used. When the plural form is used, the focus is on the characteristics of a group. For example:

What are people?

asks about the characteristics of a group of people, or of people considered as a collective, while:

What is a person?

focuses on the definition of an individual person, of a perdson taken in isolation. In some cases the plural will seem more natural, particularly when we often deal with the subject in groups:

  • What are cattle
  • What are dollars?
  • What are bacteria?

In other cases, where we tend to deal with a kind of thing one at a time, the singualr form may seem more natural:

  • What is a building?
  • What is a mood?
  • What is the sun?
  • What is an ocean?

In many cases, either form seems quite natural and one may freely use either, although the response may differ with the form.

  • What are birds? We just don't know.
    – Showsni
    Oct 15, 2022 at 16:48
  • This is a simple question with a good answer. Now, let's see how we can make it into "big thing". Just expressing a bit of annoyance...
    – Lambie
    Mar 23, 2023 at 15:16

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