pecan tree vs Carya illinoinsis

pecan tree and Carya illinoinsis both are nouns.

Word	Noun	Adjective	Verb	Adverb
pecan tree	Yes	No	No	No
Carya illinoinsis	Yes	No	No	No

As nouns, pecan tree and Carya illinoinsis are synonyms defined as:

pecan tree and Carya illinoinsis: tree of southern United States and Mexico cultivated for its nuts

Other synonyms of pecan tree include Carya illinoensis, pecan.

pecan tree (noun)	Carya illinoinsis (noun)
tree of southern United States and Mexico cultivated for its nuts	tree of southern United States and Mexico cultivated for its nuts