the pot calling the kettle black

the idiom of the day is 'the pot calling the kettle black'. so what does it mean? it means 'a situation in which one person criticizes another for a fault he/she has him/herself'. for example, A accused B for lying but A was a liar as well. in this case, B would have the right to say to A 'the pot calling the kettle black'. in mandarin, it is written as either '五十步笑百步' or '乌鸦笑猪黑'.