Sierra Nevada Mountains vs Sierra Nevada

Sierra Nevada Mountains and Sierra Nevada both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sierra Nevada Mountains	Yes	No	No	No
Sierra Nevada	Yes	No	No	No

As nouns, Sierra Nevada Mountains and Sierra Nevada are synonyms defined as:

Sierra Nevada Mountains and Sierra Nevada: a mountain range in eastern California; contains Mount Whitney

Other synonyms of Sierra Nevada Mountains include High Sierra.

Sierra Nevada Mountains (noun)	Sierra Nevada (noun)
a mountain range in eastern California; contains Mount Whitney	a mountain range in eastern California; contains Mount Whitney
	a mountain range in southern Spain along the Mediterranean coast to the east of Granada