grey alder vs alder

grey alder and alder both are nouns.

Word	Noun	Adjective	Verb	Adverb
grey alder	Yes	No	No	No
alder	Yes	No	No	No

As nouns, alder is a hypernym of grey alder; that is, alder is a word with a broader meaning than grey alder:

grey alder: native to Europe but introduced in America
alder: north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant

Other hypernyms of grey alder include alder tree.

grey alder (noun)	alder (noun)
native to Europe but introduced in America	north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant
	wood of any of various alder trees; resistant to underwater rot; used for bridges etc