class Cyanophyceae vs cyanobacteria

class Cyanophyceae and cyanobacteria both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Cyanophyceae	Yes	No	No	No
cyanobacteria	Yes	No	No	No

class Cyanophyceae (noun)	cyanobacteria (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