govern vs reign

govern is not a noun while reign is a noun.

Word	Noun	Adjective	Verb	Adverb
govern	No	No	Yes	No
reign	Yes	No	Yes	No

As verbs, reign is a hyponym of govern; that is, reign is a word with a more specific, narrower meaning than govern:

Other hyponyms of govern include throne, misgovern, dictate.

govern (noun)	reign (noun)
	royal authority; the dominion of a monarch
	the period during which a monarch is sovereign
	a period during which something or somebody is dominant or powerful

govern (verb)	reign (verb)
exercise authority over; as of nations	have sovereign power
direct or strongly influence the behavior of	be larger in number, quantity, power, status or importance
bring into conformity with rules or principles or usage; impose regulations
require to be in a certain grammatical case, voice, or mood