1. A small filament issuing from the skin of an animal, and from a bulbous root. Each filament contains a tube or hollow within, occupied by a pulp or pith, which is intended for its nutrition, and extends only to that part which is in a state of growth.
When hair means a single filament, it has a plural, hairs.
2. The collection or mass of filaments growing from the skin of an animal, and forming an integument or covering; as the hair of the head. hair is the common covering of many beasts. When the filaments are very fine and short, the collection of them is called fur. Wool, also, is a kind of hair When hair signifies a collection of these animal filaments, it has no plural.
3. Any thing very small or fine; or a very small distance; the breadth of a hair He judges to a hair that is, very exactly.
4. A trifling value. It is not worth a hair
5. Course; order; grain; the hair falling in a certain direction. [Not used.]
You go against the hair of your profession.
6. Long, straight and distinct filaments on the surface of plants; a species of down or pubescence.