drop out
英 [drɒp aʊt] 美 [drɑːp aʊt]
释义：退学;退出(比赛等);拒绝接受传统规范;离经叛道;摈弃社会习俗
例句：
He'd dropped out of high school at the age of 16
他16岁的时候就从中学退学了。
She encourages people to keep their jobs rather than dropping out to live in a commune.
她鼓励人们坚持工作而不是离经叛道地去过公社生活。
drop off
英 [ˈdrɒp ɒf] 美 [ˈdrɑːp ɔːf]
中途放下(某人);中途卸下(某物);打瞌睡;睡着;减退;减少
例句：
I must have dropped off to sleep.
我肯定是睡着了。
Just as I was dropping off, a strange thought crossed my mind.
就在我打瞌睡的时候，一个奇怪的念头闪过我的脑海。
drop-in
发音：英 [ˈdrɒp ɪn] 美 [ˈdrɑːp ɪn]
释义：adj.可随时造访的;无须预约的
例句：
It's not a drop-in replacement, and, in fact, JDOM and DOM can happily coexist.
它并不是一个简单的替代品，实际上JDOM和DOM能够愉快地并存。
But all were drawn to this drop-in workshop: Anxiety 101.
但他们都是被该中心开办的随到随加入的研讨会&焦虑症101(Anxiety101)吸引而来。
食客小蒲
