1. 过失;缺点
The demerits of something or someone are their faults or disadvantages.

1. the quality of being inadequate or falling short of perfection

e.g. they discussed the merits and demerits of her novel
he knew his own faults much better than she did

Synonym: fault

2. a mark against a person for misconduct or failure
usually given in school or armed forces

e.g. ten demerits and he loses his privileges