B2 常识；众所周知的事
a fact that everyone knows
[ + that ] It's common knowledge that they live together. 他们住在一起，这事儿尽人皆知。
It was common knowledge that she was considering moving back to Bahrain.
It was common knowledge that some of his associates had been in prison.
The animosity between them was common knowledge among the staff.
"Are you sure you want to accuse him of lying?" "Why wouldn't I? It's common knowledge."
See also: common adjective (USUAL)