stone fruit vs plum

stone fruit and plum both are nouns.

Word	Noun	Adjective	Verb	Adverb
stone fruit	Yes	No	No	No
plum	Yes	No	No	Yes

As nouns, plum is a hyponym of stone fruit; that is, plum is a word with a more specific, narrower meaning than stone fruit:

stone fruit: fleshy indehiscent fruit with a single seed: e.g. almond, peach, plum, cherry, elderberry, olive, jujube
plum: any of numerous varieties of small to medium-sized round or oval fruit having a smooth skin and a single pit

Other hyponyms of stone fruit include almond, peach, cherry, elderberry, Chinese date, Chinese jujube, jujube, olive, drupelet.

stone fruit (noun)	plum (noun)
fleshy indehiscent fruit with a single seed: e.g. almond, peach, plum, cherry, elderberry, olive, jujube	a highly desirable position or assignment
	any of numerous varieties of small to medium-sized round or oval fruit having a smooth skin and a single pit
	any of several trees producing edible oval fruit having a smooth skin and a single hard stone

stone fruit (adverb)	plum (adverb)
	exactly
	completely; used as intensifiers