filament vs rhizoid

filament and rhizoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
filament	Yes	No	No	No
rhizoid	Yes	No	No	No

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

filament: a very slender natural or synthetic fiber
rhizoid: any of various slender filaments that function as roots in mosses and ferns and fungi etc

Other hyponyms of filament include barb, cobweb, gossamer, chromatid, myofibril, myofibrilla, sarcostyle, hypha, paraphysis.

filament (noun)	rhizoid (noun)
a thin wire (usually tungsten) that is heated white hot by the passage of an electric current	any of various slender filaments that function as roots in mosses and ferns and fungi etc
a threadlike structure (as a chainlike series of cells)
the stalk of a stamen
a very slender natural or synthetic fiber