Alnus vulgaris vs common alder

Alnus vulgaris and common alder both are nouns.

Word	Noun	Adjective	Verb	Adverb
Alnus vulgaris	Yes	No	No	No
common alder	Yes	No	No	No

As nouns, Alnus vulgaris and common alder are synonyms defined as:

Alnus vulgaris and common alder: medium-sized tree with brown-black bark and woody fruiting catkins; leaves are hairy beneath

Other synonyms of Alnus vulgaris include Alnus glutinosa, European black alder.

Alnus vulgaris (noun)	common alder (noun)
medium-sized tree with brown-black bark and woody fruiting catkins; leaves are hairy beneath	medium-sized tree with brown-black bark and woody fruiting catkins; leaves are hairy beneath