Learner's definition of BREAKDOWN
1 : a failure of a machine to function : an occurrence in which a machine (such as a car) stops working
2 a [count] : the failure of a relationship or of an effort to discuss something
b : a failure that prevents a system from working properly
There has been a breakdown of/in negotiations. [=negotiations have broken down; negotiations have failed]
Both sides are to blame for the breakdown in communication.
The irretrievable breakdown of a marriage can be grounds for divorce.
3 [count] : a sudden failure of mental or physical health that makes someone unable to live normally 4 : the process or result of showing the different parts of something in order to understand it more clearly
5 [noncount] : the process or result of separating a substance into simpler parts
the breakdown of water into hydrogen and oxygen
observing cell/tissue/protein breakdown
a substance that resists breakdown
— see also break down at 1break