Main Entry: di·am·e·ter

Pronunciation: \dī-ˈa-mə-tər\

Function: noun

Etymology: Middle English diametre, from Middle French, from Latin diametros, from Greek, from dia- + metron measure — more at measure

Date: 14th century

1 : a chord passing through the center of a figure or body
2 : the length of a straight line through the center of an object
3 : a unit of enlargement used with a number to indicate magnification by a lens or optical system <an object one millimeter wide magnified 40 diameters appears 40 millimeters wide>

— di·am·e·tral \-ˈa-mə-trəl\ adjective