authority vs muscle

authority and muscle both are nouns.

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

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

authority: the power or right to give orders or make decisions
muscle: authority or power or force (especially when used in a coercive way)

Other hyponyms of authority include power of appointment, carte blanche, command, imperium, lordship, sovereignty.

authority (noun)	muscle (noun)
the power or right to give orders or make decisions	possessing muscular strength
official permission or approval	authority or power or force (especially when used in a coercive way)
freedom from doubt; belief in yourself and your abilities	one of the contractile organs of the body
an authoritative written work	animal tissue consisting predominantly of contractile cells
an administrative unit of government	a bully employed as a thug or bodyguard
an expert whose views are taken as definitive
(usually plural) persons who exercise (administrative) control over others

authority (verb)	muscle (verb)
	make one's way by force