class Cyanophyceae vs blue-green algae

class Cyanophyceae and blue-green algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Cyanophyceae	Yes	No	No	No
blue-green algae	Yes	No	No	No

class Cyanophyceae (noun)	blue-green algae (noun)
photosynthetic bacteria found in fresh and salt water, having chlorophyll a and phycobilins; once thought to be algae: blue-green algae	predominantly photosynthetic prokaryotic organisms containing a blue pigment in addition to chlorophyll; occur singly or in colonies in diverse habitats; important as phytoplankton