What kind of noun is hair?

"Hair" can be both a countable noun and an uncountable noun, depending on how it's used.

Countable Noun:

* When referring to individual strands or groups of strands: "I found a few hairs on my shirt." "She has long, blonde hairs."

Uncountable Noun:

* When referring to hair as a general mass: "I need to cut my hair." "He has dark hair."

So, it depends on the context!