endorsement vs imprimatur

endorsement and imprimatur both are nouns.

Word	Noun	Adjective	Verb	Adverb
endorsement	Yes	No	No	No
imprimatur	Yes	No	No	No

As nouns, endorsement and imprimatur are synonyms defined as:

Other synonyms of endorsement include countenance, indorsement, sanction, warrant.

endorsement (noun)	imprimatur (noun)
the act of endorsing	formal and explicit approval
formal and explicit approval
a promotional statement (as found on the dust jackets of books)
a speech seconding a motion
a signature that validates something