approval vs indorsement

approval and indorsement both are nouns.

Word	Noun	Adjective	Verb	Adverb
approval	Yes	No	No	No
indorsement	Yes	No	No	No

As nouns, indorsement is a hyponym of approval; that is, indorsement is a word with a more specific, narrower meaning than approval:

approval (noun)	indorsement (noun)
the formal act of approving	the act of endorsing
a message expressing a favorable opinion	formal and explicit approval
a feeling of liking something or someone good	a promotional statement (as found on the dust jackets of books)
acceptance as satisfactory	a speech seconding a motion
	a signature that validates something