Credentials vs Certified - What's the difference?

As a noun credentials

is plural of lang=en: Documentary evidence of someone's right to credit or authority, especially such a document given to an ambassador by a country.

past tense of certify.

(head)

: Documentary evidence of someone's right to credit or authority, especially such a document given to an ambassador by a country.

* English nouns

(head)

(certify)

to attest to as the truth or meeting a standard

* (to attest as to) attest, witness, vouch for, approve, confirm

* certifiable * decertify