Is hair a plural noun or singular noun?

Answer 1

The noun 'hair' is an uncountable noun as a word for a substance that grows from human or animal skin.
The noun 'hair' is a count noun as a word for the strands or shafts of this substance.
The plural noun is hairs.

Examples:
"Your hair is a mess!" (uncountable)
"You have cat hairs on your coat." (countable)

Answer 2

When referring to a substance used to change the color of something, it's dye, not die. The plural form is dyes.

Answer 3

The plural of hair can be hair or hairs depending on its use - a full head of hair or two hairs were found.

Answer 4

Des cheveux if you're talking about head, des poils for other parts of the body

Answer 5

Hair is both plural and singular. While you can refer to a single hair, or to many individual hairs, the uncountable plural for hairs is also hair.