hair

Concise Oxford English Dictionary © 2008 Oxford University Press:
hair/heə(r)/

▶noun

• 1 any of the fine thread-like strands growing from the skin of mammals and other animals, or from the epidermis of a plant.

  ■ hairs collectively, especially those on a person's head.

• 2 a very small quantity or extent.

– phrases
hair of the dog informal an alcoholic drink taken to cure a hangover. [from hair of the dog that bit you, formerly recommended as an effective remedy for the bite of a mad dog.]
a hair's breadth a very small margin.
in (or out of) someone's hair informal annoying (or ceasing to annoy) someone.
keep your hair on! Brit. informal stay calm.
let one's hair down informal behave uninhibitedly.
make someone's hair stand on end alarm someone.
not turn a hair remain apparently unmoved.
split hairs make overfine distinctions.

– derivatives
-haired adjective,
hairless adjective.

– origin OE hǣr, of Gmc origin.