Student or Learner
what is the plural of hair? are these sentences correct? 1)that is a hair. 2)those are hairs.
Both your sentences are grammatically correct. However, "hair" can be both countable and uncountable. As a countable noun, the plural is "hairs". If you are talking about all the "hairs" on your head, it's just your "hair".
I can see some red hairs on the sofa. Do you have a red dog?
I can see that you have red hair. Is it natural or do you dye it?
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.