mammary gland vs bosom

mammary gland and bosom both are nouns.

Word	Noun	Adjective	Verb	Adverb
mammary gland	Yes	No	No	No
bosom	Yes	No	Yes	No

As nouns, bosom is a hyponym of mammary gland; that is, bosom is a word with a more specific, narrower meaning than mammary gland:

mammary gland: milk-secreting organ of female mammals
bosom: either of two soft fleshy milk-secreting glandular organs on the chest of a woman

Other hyponyms of mammary gland include dug, bag, udder, boob, breast, knocker, tit, titty.

mammary gland (noun)	bosom (noun)
milk-secreting organ of female mammals	a close affectionate and protective acceptance
	cloth that covers the chest or breasts
	either of two soft fleshy milk-secreting glandular organs on the chest of a woman
	a person's breast or chest
	the locus of feelings and intuitions
	the chest considered as the place where secret thoughts are kept

mammary gland (verb)	bosom (verb)
	hold (someone) tightly in your arms, usually with fondness
	hide in one's bosom