hen vs mother hen

hen and mother hen both are nouns.

Word	Noun	Adjective	Verb	Adverb
hen	Yes	No	No	No
mother hen	Yes	No	No	No

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

Other hyponyms of hen include cackler, brood hen, broody, broody hen, setting hen, sitter, layer, pullet.

hen (noun)	mother hen (noun)
adult female chicken	a hen with chicks
adult female bird	a person who cares for the needs of others (especially in an overprotective or interfering way)
female of certain aquatic animals e.g. octopus or lobster
flesh of an older chicken suitable for stewing