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.
一般的,set out还有陈述说明的意思,set off还有使爆炸的意思
set out to do sth