common tobacco vs tobacco

common tobacco and tobacco both are nouns.

Word	Noun	Adjective	Verb	Adverb
common tobacco	Yes	No	No	No
tobacco	Yes	No	No	No

As nouns, tobacco is a hypernym of common tobacco; that is, tobacco is a word with a broader meaning than common tobacco:

common tobacco: tall erect South American herb with large ovate leaves and terminal clusters of tubular white or pink flowers; cultivated for its leaves
tobacco: aromatic annual or perennial herbs and shrubs

Other hypernyms of common tobacco include tobacco plant.

common tobacco (noun)	tobacco (noun)
tall erect South American herb with large ovate leaves and terminal clusters of tubular white or pink flowers; cultivated for its leaves	leaves of the tobacco plant dried and prepared for smoking or ingestion
	aromatic annual or perennial herbs and shrubs