when: [OE] When was formed from the ancient interrogative base *qwo- (source also of English what, who, etc) and a nasal suffix which also appears in then. From the same ancestor, but with an additional dental suffix, came Latin quando ‘when’, source of English quandary. => quandary
when (adv.)
Old English hw?nne, hwenne, hwonne, from Proto-Germanic *hwan- (cognates: Old Saxon hwan, Old Frisian hwenne, Middle Dutch wan, Old High German hwanne, German wann "when," wenn "if, whenever"), from pronominal stem *hwa-, from PIE interrogative base *kwo- (see who). Equivalent to Latin quom, cum. As a conjunction in late Old English. Say when "tell me when to stop pouring you this drink" is from 1889.
實(shí)用例句
1. The best thing to do when entering unknown territory is smile.
踏入未知地帶最好的對(duì)策就是微笑。
來(lái)自美劇《凱莉日記》
2. When life gets hard and you want to give up, remember that life is full of ups and downs, and without the downs, the ups would mean nothing.