副词 adv. 1.什么时候 2.（用于时间的表达方式之后）在那时, 其时 3.其时；当时；当场
连接词 conj. 1.引导时间状语从句。如：Don’t be afraid of asking for help when it is needed.
2.类似并列连词，表at that time, 常用于be about to do ... when, hardly...when等句型中。如：
We were swimming in the lake when suddenly the storm started.
3.表原因，同since。如：Why do you want a new job when you’ve got such a good one already?
4.连接副词，用于名词性从句中。如：I remember when this used to be a quiet village.
5.关系副词，用于定语从句中。如：The film brought the hours back to me when I was taken good care of in that far-away village.
6.whenever引导名词性从句和让步状语从句。如：You can eat food free in my restaurant whenever you like.
7.表让步，同even if.如：The enemy held out when they must have known there was no hope.
代词 pron.
1.什么时候
2.那时
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