hair vs hair's-breadth

hair and hair's-breadth both are nouns.

Word	Noun	Adjective	Verb	Adverb
hair	Yes	No	No	No
hair's-breadth	Yes	No	No	No

As nouns, hair and hair's-breadth are synonyms defined as:

Other synonyms of hair include hairsbreadth, whisker.

hair (noun)	hair's-breadth (noun)
a filamentous projection or process on an organism	a very small distance or space
cloth woven from horsehair or camelhair; used for upholstery or stiffening in garments
a covering for the body (or parts of it) consisting of a dense growth of threadlike structures (as on the human head); helps to prevent heat loss
any of the cylindrical filaments characteristically growing from the epidermis of a mammal
filamentous hairlike growth on a plant
a very small distance or space