yellow-green algae vs algae

yellow-green algae and algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellow-green algae	Yes	No	No	No
algae	Yes	No	No	No

As nouns, algae is a hypernym of yellow-green algae; that is, algae is a word with a broader meaning than yellow-green algae:

yellow-green algae: any alga of the division Chrysophyta with its chlorophyll masked by yellow pigment
algae: primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves

Other hypernyms of yellow-green algae include alga.

yellow-green algae (noun)	algae (noun)
any alga of the division Chrysophyta with its chlorophyll masked by yellow pigment	primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves