mammary gland vs breast

mammary gland and breast both are nouns.

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

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

mammary gland: milk-secreting organ of female mammals
breast: 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, bosom, knocker, tit, titty.

mammary gland (noun)	breast (noun)
milk-secreting organ of female mammals	the part of an animal's body that corresponds to a person's chest
	either of two soft fleshy milk-secreting glandular organs on the chest of a woman
	the front of the trunk from the neck to the abdomen
	meat carved from the breast of a fowl

mammary gland (verb)	breast (verb)
	confront bodily
	reach the summit (of a mountain)
	meet at breast level