authority vs approver

authority and approver both are nouns.

Word	Noun	Adjective	Verb	Adverb
authority	Yes	No	No	No
approver	Yes	No	No	No

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

authority: (usually plural) persons who exercise (administrative) control over others
approver: an authority with power to approve

authority (noun)	approver (noun)
the power or right to give orders or make decisions	an authority with power to approve
official permission or approval
freedom from doubt; belief in yourself and your abilities
an authoritative written work
an administrative unit of government
an expert whose views are taken as definitive
(usually plural) persons who exercise (administrative) control over others