- when 指某特定時間點。
- 用法一：When S ＋ V-ed..., S ＋ was ／ were ＋ V-ing...= S ＋ was ／ were ＋ V-ing... when S ＋ V-ed...
- 如：When Mom came home, I was doing my homework. = I was doing my homework when Mom came home.
- （媽媽回家時，我正在寫功課。）
- 用法二：When S ＋ V-ed..., S ＋ V-ed... = S ＋ V-ed... when S ＋ V-ed...
- 如：When the teacher appeared at the classroom door, all the students became quiet. = All the students became quiet when the teacher appeared at the classroom door.
- （老師出現在教室門口時，所有的學生都安靜了下來。）
- 用法三：When S ＋ was ／ were ＋ V-ing..., S ＋ V-ed...= S ＋ V-ed... when S ＋ was ／ were ＋ V-ing...
- 如：When I was walking home from school, I saw a wallet on the sidewalk.= I saw a wallet on the sidewalk when I was walking home from school.（我正從學校走路回家時，在人行道上看到一個錢包。）