break down和break up都表示“分解”时,怎么区别?

eak down:1) if a car or a machine break down,it stops working.2)to fail.3) if someone break down,they start crying.4)if you break down a door,you hit it so hard that it breaks and falls to the ground.5) if a substance breaks down,or if something breaks it down,it changes or separate into smaller parts as a result of a chemical process
break up:1)to separate something into smaller parts.2) if somethingbreaks up,or if you break it up,it breaks into small pieces.3)to end a relationship with a husband,wife.4) to stop a fight or argument.5) if a meeting or party breaks up,people start to leave.6) when a school break up,it close for a holiday.