铅是早在古代就已知的金属之一。Lead was one of the metals known to the ancient world.水银是一种已知的有毒物质。Mercury is a known poison.人们通常从已知的事实中推断未知的事实.People usually infer an unknown fact from a known fact....

“已知的”的英语可以翻译为：foregone，known ...