Cornus obliqua vs dogwood

Cornus obliqua and dogwood both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cornus obliqua	Yes	No	No	No
dogwood	Yes	No	No	No

As nouns, dogwood is a hypernym of Cornus obliqua; that is, dogwood is a word with a broader meaning than Cornus obliqua:

Cornus obliqua: shrub of eastern North America closely resembling silky cornel
dogwood: a tree of shrub of the genus Cornus often having showy bracts resembling flowers

Other hypernyms of Cornus obliqua include cornel, dogwood tree.

Cornus obliqua (noun)	dogwood (noun)
shrub of eastern North America closely resembling silky cornel	a tree of shrub of the genus Cornus often having showy bracts resembling flowers
	hard tough wood of any dogwood of the genus Cornus; resembles boxwood