to say in a formal or official way, usually in the form of an official document, that something is true or correct

[ + (that) ] I hereby certify (that) the above information is true and accurate. 兹证明上述情况属实准确无误。

[ + noun/adj ] The man was certified (as) dead on arrival at the hospital.

The meat has been certified (as) fit for human consumption. 已证实该肉品适合人食用。

The driver holds a commercial license and is certified to transport hazardous materials.

to say officially that someone is mentally ill

As a young man, he had been certified and sent to a hospital for the mentally ill. 他年轻时被证明患有精神病，并被送到了精神病院。