lengthen
/ˈleŋkθən/verb
1- make or become longer使变长：
with obj. she lengthened her stride to catch him up她迈开脚步以便追上他
no obj. in the spring when the days are lengthening在白天越来越长的春天
as adj. lengthening the lengthening shadows.渐长的影子。
1.1
- with obj. Prosody & Phonetics make (a vowel or syllable) long【诗韵, 语音】使（元音, 音节）拖长。