LAUGHTER  , the visible and audible expression of mirth,

pleasure or the sense of the ridiculous by movements of the facial muscles and inarticulate sounds (see COMEDY, PLAY and HuMouR) . The O . Eng. hleahtor is formed from hleahhan, to laugh, a common Teutonic word; cf . Ger. lachen, Goth. hlahjan, Icel. hlaeja, &c . These are in origin echoic or imitative words, to be referred to a Tent. base hlah-, Indo-Eur. kark-, to make a noise; Skeat (Etym . Dict., 1898) connects ultimately Gr. xX roew, to cluck like a hen, Kp4eLv, to croak, &c . A gentle and inaudible form of laughter expressed by a movement of the lips and by the eyes is a " smile." This is a comparatively late word in English, and is due to Scandinavian influence; cf . Swed. smila; it is ultimately connected with Lat. mirari, to wonder, and probably with Gr . µeTos .