precious stone vs ruby

precious stone and ruby both are nouns.

Word	Noun	Adjective	Verb	Adverb
precious stone	Yes	No	No	No
ruby	Yes	Yes	No	No

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

precious stone: a precious or semiprecious stone incorporated into a piece of jewelry
ruby: a transparent piece of ruby that has been cut and polished and is valued as a precious gem

Other hyponyms of precious stone include crown jewel, solitaire, diamond, pearl, emerald, sapphire.

precious stone (noun)	ruby (noun)
a precious or semiprecious stone incorporated into a piece of jewelry	a deep and vivid red color
	a transparent piece of ruby that has been cut and polished and is valued as a precious gem
	a transparent deep red variety of corundum; used as a gemstone and in lasers

precious stone (adjective)	ruby (adjective)
	of a color at the end of the color spectrum (next to orange); resembling the color of blood or cherries or tomatoes or rubies