Plural: acnes

ETYM New Lat., prob. a corruption of Greek akme a point.
An inflammatory disease involving the sebaceous glands of the skin; characterized by papules or pustules or comedones.
Skin eruption, mainly occurring among adolescents and young adults, caused by inflammation of the sebaceous glands which secrete an oily substance (sebum), the natural lubricant of the skin. Sometimes the openings of the glands become blocked, causing the formation of pus-filled swellings. Teenage acne is seen mainly on the face, back, and chest.
There are other less common types of acne, sometimes caused by contact with irritant chemicals.