Definition of “certify” - Learner’s Dictionary

certify

verb [ T ] uk us /ˈsɜːtɪfaɪ/
TRUTH formal

to say in a formal or official way that something is true or correct:

[ + (that) ] I certify that the information I have given is true.
She was certified dead on arrival at the hospital.
CERTIFICATE

to give someone a certificate to say that they have completed a course of study:

a certified accountant
HEALTH

to say officially that someone has a mental illness

(Definition of “certify” from the Cambridge Learner's Dictionary © Cambridge University Press)