set out和set off都有出发的意思，set off更含开始(旅行、赛跑等）的意思。例：what time are you planning to set off tomorrow？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 off
英：[set ɒf]；美：[set ɔːf]
动身；出发；启程；引爆（炸弹）；拉响（警报等）；引发；触发；激起
set off的用法
（1）To give rise to；cause to occur:发生：引起；导致发生：set off a chemical reaction。发生化学反应
（2）To cause to explode：爆炸：引起爆炸：set off a bomb。炸弹爆炸
（3）To indicate as being different；distinguish:区分：指出不同；区分：
features setting him off from the crowd。使他与人群分开的特征
（4）To direct attention to by contrast；accentuate：强调：通过对比引起注意；强调：set off a passage with italics。用斜体字强调一段
（5）To start on a journey：开始旅程：set off for Europe。
set out
英：[set aʊt]；美：[set aʊt]
动身；出发；启程；开始；着手；安排；摆放；陈列；（清晰而有条理地）陈述，阐述，说明
set out的用法
1．leave on a journey or voyage启程或启航
He will set out tomorrow on his journey to Beijing．他明天动身去北京。
2．attempt试图
He set out to do a lot of things，but didn't succeed．他原打算做许多事，但都未成功。
3．plant in the ground种植
The gardener set out some tomato seedlings．这位园丁种植了些西红柿苗。
4．display陈列；布置
The goods are set out in the shop window．商品陈列在商店的橱窗里。
5．start to do sth．开始；着手
They set out to perform the opera tion．他们开始动手术。
6．state；describe；define陈述；叙述；说明
He set out his ideas in simple Eng lish．他用简单的英文表达了他的想法。
