when的意思:1,什么时候,用于提问,如:When did you last see him? 2,在那时,用于时间的表达方式之后,如：Sunday is the only day shen I can relax. 3,在……之后,如：Call me when you have finshed. 4,一……就……,如：He had just drifted lff to sleep when the phone rang. 5,当……时候,如：When I was young,I had a lovely cat. until的意思：到……时,到……为止,如：Let us wait until the rain stops.
