abolish 正式用词，指彻底废除某种制度、规章或习俗。
abolish slavery
废除奴隶制
abolish the system of exploitation of man by man
消灭人剥削人的制度
These superstitious practices should be abolished as soon as possible.
这些迷信做法应尽早取消。
cancel 用法广泛，多指取消债务、合同、证书、比赛、旅行、计划或约会等。
Passengers who cancel their reservations will forfeit their deposit
旅客取消预订票者, 定金不予退还。
They threatened to cancel the whole project at a stroke
他们扬言要一下子取消整个项目。
If one side failed to honor the contract, the other side should be entitled to cancel it
如合同一方不按合同条款行事，另一方则有权中止合同。
I cancelled many unnecessary words in my manuscript.
我把我原稿许多不需要的字删去了。
repeal 书面用词，指撤销立法机关通过的协议、法案或法律等。
The Congress decided to repeal the law
议会决定废除那项法令。
Mps are pressing for the repeal of the immigration act
下院议员正在施加压力使移民法得以废止。
Many voted for the repeal of that property law
许多人投票赞成废止那项财产法。
