cassia vs Cinnamomum cassia

cassia and Cinnamomum cassia both are nouns.

Word	Noun	Adjective	Verb	Adverb
cassia	Yes	No	No	No
Cinnamomum cassia	Yes	No	No	No

As nouns, cassia and Cinnamomum cassia are synonyms defined as:

cassia and Cinnamomum cassia: Chinese tree with aromatic bark; yields a less desirable cinnamon than Ceylon cinnamon

Other synonyms of cassia include cassia-bark tree.

cassia (noun)	Cinnamomum cassia (noun)
any of various trees or shrubs of the genus Cassia having pinnately compound leaves and usually yellow flowers followed by long seedpods	Chinese tree with aromatic bark; yields a less desirable cinnamon than Ceylon cinnamon
Chinese tree with aromatic bark; yields a less desirable cinnamon than Ceylon cinnamon