protoctist vs algae

protoctist and algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
protoctist	Yes	No	No	No
algae	Yes	No	No	No

As nouns, algae is a hyponym of protoctist; that is, algae is a word with a more specific, narrower meaning than protoctist:

protoctist: any of the unicellular protists
algae: primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves

Other hyponyms of protoctist include protozoan, protozoon, alga.

protoctist (noun)	algae (noun)
any of the unicellular protists	primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves