genus Alnus vs alder tree

genus Alnus and alder tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Alnus	Yes	No	No	No
alder tree	Yes	No	No	No

genus Alnus (noun)	alder tree (noun)
alders	north temperate shrubs or trees having toothed leaves and conelike fruit; bark is used in tanning and dyeing and the wood is rot-resistant