fibril vs sarcostyle

fibril and sarcostyle both are nouns.

Word	Noun	Adjective	Verb	Adverb
fibril	Yes	No	No	No
sarcostyle	Yes	No	No	No

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

fibril: a very slender natural or synthetic fiber
sarcostyle: one of many contractile filaments that make up a striated muscle fiber

Other hyponyms of fibril include barb, cobweb, gossamer, chromatid, myofibril, myofibrilla, rhizoid, hypha, paraphysis.

fibril (noun)	sarcostyle (noun)
a very slender natural or synthetic fiber	one of many contractile filaments that make up a striated muscle fiber