skin eruption common during puberty, 1813, from Modern Latin, from aknas, a 6c. Latin clerical misreading of Greek akmas, accusative plural of akmē "point" (see acme), from PIE root *ak- "be sharp, rise (out) to a point, pierce." The "pointed" pimples are the source of the medical use.

also air-line, 1813, "beeline, straight line between two points on the earth's surface" (as through the air, rather than over terrain), from air (n.1) + line (n.). From 1853 and in later 19c. especially in reference to railways that ran directly between big cities in the U.S. instead of meandering from town to town in search of stock subscriptions as early railways typically did. Meaning "public aircraft transportation company" is from 1914.

"including everything or everyone," 1813, from all + inclusive. Related: All-inclusively; all-inclusiveness.

principal language of Ethiopia, 1813, from Amhara, name of a central province in Ethiopia. It is in the Semitic family.

also anti-theist, "one opposed to belief in the existence of a god," 1813; see anti- "opposite to, against" + theist. Related: Antitheistic. Greek antitheos meant "equal to the gods, god-like," from a different sense of anti.

"kiwi," zoological name for the flightless birds of New Zealand, 1813, Modern Latin, from Greek a- "without" (see a- (3)) + pteryx "wing" (from PIE root *pet- "to rush, to fly").

"a student of the science of life," 1813, from biology + -ist. The earliest use is in reference to human life (with the Greek sense of bios, for which see bio-); in its modern scientific sense, "one skilled in or a student of the discipline of biology," by 1874. Biologian is attested from 1865.

"land forming a border or frontier; an uncertain intermediate region or space," often figurative, 1813, from border (n.) + land (n.).

"pertaining to the cheek," 1813, from Latin bucca "cheek," especially when puffed out (later "mouth"); see bouche.

also Cassegrainian, in reference to a type of reflecting telescope, 1813, named for 17c. French priest and teacher Laurent Cassegrain, who described it in a journal article in 1672.