black birch vs birch

black birch and birch both are nouns.

Word	Noun	Adjective	Verb	Adverb
black birch	Yes	No	No	No
birch	Yes	Yes	Yes	No

As nouns, birch is a hypernym of black birch; that is, birch is a word with a broader meaning than black birch:

black birch: birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark
birch: any betulaceous tree or shrub of the genus Betula having a thin peeling bark

Other hypernyms of black birch include birch tree.

As nouns, birch is a hypernym of black birch; that is, birch is a word with a broader meaning than black birch:

black birch: common birch of the eastern United States having spicy brown bark yielding a volatile oil and hard dark wood used for furniture
birch: any betulaceous tree or shrub of the genus Betula having a thin peeling bark

Other hypernyms of black birch include birch tree.

black birch (noun)	birch (noun)
birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark	a switch consisting of a twig or a bundle of twigs from a birch tree; used to hit people as punishment
common birch of the eastern United States having spicy brown bark yielding a volatile oil and hard dark wood used for furniture	any betulaceous tree or shrub of the genus Betula having a thin peeling bark
	hard close-grained wood of any of various birch trees; used especially in furniture and interior finishes and plywood

black birch (adjective)	birch (adjective)
	consisting of or made of wood of the birch tree

black birch (verb)	birch (verb)
	whip with a birch twig