valley vs ravine

valley and ravine both are nouns.

Word	Noun	Adjective	Verb	Adverb
valley	Yes	No	No	No
ravine	Yes	No	No	No

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

valley: a long depression in the surface of the land that usually contains a river
ravine: a deep narrow steep-sided valley (especially one formed by running water)

Other hyponyms of valley include dale, glen, gully, holler, hollow, nullah, rift valley.

valley (noun)	ravine (noun)
a long depression in the surface of the land that usually contains a river	a deep narrow steep-sided valley (especially one formed by running water)