set out和set off都有出发的意思,区别:
set off更含开始(旅行、赛跑等）的意思,
例：what time are you planning to set off tommorrow?你明天打算几点钟启程?
they've set off on a journey round the world.
他们已经开始环游世界.
set out意思是从某地出发上路
例：she set out at dawn.她天一亮就动身了.
另外,set out to do sth是开始／着手干某事
而,set sb off doing sth是使某人开始干某事