a hair that does not emerge from the follicle but remains embedded in the skin (usually causing inflammation)

a hair that curls and

a hair that curls into the side wall of the hair follicle or into the skin surface instead of growing straight out of the follicle opening

a hair that does not grow straight out of the follicle opening

See folliculitis.

A hair that does not break the surface of the skin, and grows back inward. Can be severe and cause inflammation, soreness and infection.

Ingrown hair is a condition where the hair curls back or grows sideways into the skin. It may or may not be accompanied by an infection of the hair follicle (folliculitis) or "razor bumps" (Pseudofolliculitis barbae). It most commonly appears in areas where the skin is shaved (beard, legs), but can appear anywhere.