western vs western sandwich

western and western sandwich both are nouns.

Word	Noun	Adjective	Verb	Adverb
western	Yes	Yes	No	No
western sandwich	Yes	No	No	No

As nouns, western and western sandwich are synonyms defined as:

western (noun)	western sandwich (noun)
a sandwich made from a western omelet	a sandwich made from a western omelet

western (adjective)	western sandwich (adjective)
relating to or characteristic of the western parts of the world or the West as opposed to the eastern or oriental parts
of or characteristic of regions of the United States west of the Mississippi River
lying toward or situated in the west
of wind; from the west