root cellar vs cellar

root cellar and cellar both are nouns.

Word	Noun	Adjective	Verb	Adverb
root cellar	Yes	No	No	No
cellar	Yes	No	No	No

As nouns, root cellar and cellar are synonyms defined as:

root cellar (noun)	cellar (noun)
an excavation where root vegetables are stored	the lowermost portion of a structure partly or wholly below ground level; often used for storage
	storage space where wines are stored
	an excavation where root vegetables are stored