oil vs walnut oil

oil and walnut oil both are nouns.

Word	Noun	Adjective	Verb	Adverb
oil	Yes	No	Yes	No
walnut oil	Yes	No	No	No

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

oil (noun)	walnut oil (noun)
oil paint containing pigment that is used by an artist	oil from walnuts
any of a group of liquid edible fats that are obtained from plants
a slippery or viscous liquid or liquefiable substance not miscible with water
a dark oil consisting mainly of hydrocarbons

oil (verb)	walnut oil (verb)
administer an oil or ointment to; often in a religious ceremony of blessing
cover with oil, as if by rubbing