Cassia roxburghii vs horse cassia

Cassia roxburghii and horse cassia both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cassia roxburghii	Yes	No	No	No
horse cassia	Yes	No	No	No

As nouns, Cassia roxburghii and horse cassia are synonyms defined as:

Cassia roxburghii and horse cassia: East Indian tree having long pods containing a black cathartic pulp used as a horse medicine

Other synonyms of Cassia roxburghii include Cassia marginata.

Cassia roxburghii (noun)	horse cassia (noun)
East Indian tree having long pods containing a black cathartic pulp used as a horse medicine	tropical American semi-evergreen tree having erect racemes of pink or rose-colored flowers; used as an ornamental
	East Indian tree having long pods containing a black cathartic pulp used as a horse medicine