(Science: geometry) Nine points circle, a circle so related to any given triangle as to pass through the three points in which the perpendiculars from the angles of the triangle upon the opposite sides (or the sides produced) meet the sides. It also passes through the three middle points of the sides of the triangle and through the three middle points of those parts of the perpendiculars that are between their common point of meeting and the angles of the triangle. The circle is hence called the nine points or six points circle.
Origin: OE. Nine, nihen, AS. Nigon, nigan; akin to D. & LG. Negen, OS. & OFries. Nigun, OHG. Niun, G. Neun, Icel. Niu, sw. Nio, Dan. Ni, Goth. Niun, Ir. & Gael. Naoi, W. Naw, L. Novem, gr, Skr. Navan; of unknown origin. 307. Cf. Novembeer.