[mass noun]the lengthening of something 拉长,延长,延伸 ■a part of a line formed by lengthening; a continuation 延长线,延长部分 ■the amount of extension of an object under stress, usually expressed as a percentage of the original length 延伸率 ■(Astronomy)the angular separation of a planet from the sun or of a satellite from a planet, as seen by an observer (天文)距角;大距
语源
late Middle English: from late Latin elongatio(n-), from elongare 'place at a distance' (see elongate)