Hair or hairs

Hair is both countable and uncountable.

If you talk about the hair on your head or body it is uncountable.

  • He needs to get his hair cut.
  • Do you know how to remove unwanted body hair?

If you talk about a few hairs it is countable.

  • You have two blonde hairs on your jacket.
  • The police found a single human hair on the knife.