breast vs bosom

breast and bosom both are nouns.

Word	Noun	Adjective	Verb	Adverb
breast	Yes	No	Yes	No
bosom	Yes	No	Yes	No

As nouns, breast and bosom are synonyms defined as:

breast and bosom: either of two soft fleshy milk-secreting glandular organs on the chest of a woman

Other synonyms of breast include boob, knocker, tit, titty.

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

breast (noun)	bosom (noun)
the part of an animal's body that corresponds to a person's chest	a close affectionate and protective acceptance
either of two soft fleshy milk-secreting glandular organs on the chest of a woman	cloth that covers the chest or breasts
the front of the trunk from the neck to the abdomen	either of two soft fleshy milk-secreting glandular organs on the chest of a woman
meat carved from the breast of a fowl	a person's breast or chest
	the locus of feelings and intuitions
	the chest considered as the place where secret thoughts are kept

breast (verb)	bosom (verb)
confront bodily	hold (someone) tightly in your arms, usually with fondness
reach the summit (of a mountain)	hide in one's bosom
meet at breast level