monarch vs head of state

monarch and head of state both are nouns.

Word	Noun	Adjective	Verb	Adverb
monarch	Yes	No	No	No
head of state	Yes	No	No	No

As nouns, head of state is a hypernym of monarch; that is, head of state is a word with a broader meaning than monarch:

monarch: a nation's ruler or head of state usually by hereditary right
head of state: the chief public representative of a country who may also be the head of government

Other hypernyms of monarch include chief of state, ruler, swayer.

monarch (noun)	head of state (noun)
large migratory American butterfly having deep orange wings with black and white markings; the larvae feed on milkweed	the chief public representative of a country who may also be the head of government
a nation's ruler or head of state usually by hereditary right