Grammar Correction

[Fatemah]

Hello everyone, I hope you all are doing well.
I have a question that what is the difference between:
“Who’s and Whose” and when and who to use them.
One more question:
Which word is correct? “Hair or Hairs
Some people say hair can never be plural but I have read many lifestyle and health blog posts where they use “hairs”

[ichkeria]

“Who’s” is short for “who is”
“Whose” means “of whom”
Of course “hair” can be plural but it depends what you want to say
“She plucked two hairs from her hair”

[calmck]

WHO's is who is example Who is coming? Who's coming?

Whose asking who something belongs to. Whose is that hat?

[JimF]

Who's is an abbreviation for "who is" or "who has"
Whose = "belonging to whom.

Who's playing tonight?
Who's been eating my porridge?

The team who's playing tonight might be late.
The team whose bus broke down might be late tonight.

Hair, is usually non-countable so the singular is used.

I don't have much hair left, not I don't have many hair left.

Hairs is rare - use hair and you'll be fine.

[New Judge]

"Who's" is an abbreviation for "who is". Example: "Who's coming to the pub for a drink?"

"Whose" is a pronoun most usually used to denote the possession of something. Example "Whose round is it?"

"Hair" is usually used to denote an area of hair. Example: The man had a chest which was covered in hair.

"Hairs" can be used as a plural when describing the number of individual hairs. Example: "I only had five hairs left on my head and three of them have fallen out."

[Buenchico]

"Who's" is short for "who is", whereas 'whose" is used to indicated ownership.

So, for example,
"Mary is the contestant who's sure to win".
[Try putting "who is" in that sentence and you'll see that it fits]

. . . BUT
"Whose turn is is to pay for lunch?"
[Try putting "who is" in that sentence and you'll see that it DOESN'T fit].

So, if in doubt, the test is to try substituting the term that you were thinking of using with "who is".

If "who is" fits, you can use "who's" to replace it.

If "who is" doesn't fit, it must be "whose" that you require in your sentence.

Each of the large number of things growing on your head is a 'hair' (singular). In total, most people have about 100,000 'hairs' (plural) up there. However the entire mass is simple known as that person's 'hair' (singular).

Sometimes there can be a bit of an overlap in the terminology. For example, see this picture:
https://images.news18.com/ibnlive/uploads/2021/07/1627624394_hair-loss-1600x1200.jpg
The woman could be saying "Look at all the HAIRS on this brush" OR "Look at all the HAIR on this brush". BOTH are correct. (In the first case, she's referring to lots of single hairs. In the second, she's referring to the mass as a whole). However she'd only refer to what's on top of her head as her 'hair' (not 'hairs'), meaning all of it, if she went to a beauty salon and said "I think that my hair needs cutting".

[Old_Geezer]

To add to other answers, when I was at secondary school, the use of "hairs" rather than "hair" tended to imply a reference to hair that grew after reaching puberty.