actin vs F-actin

actin and F-actin both are nouns.

Word	Noun	Adjective	Verb	Adverb
actin	Yes	No	No	No
F-actin	Yes	No	No	No

As nouns, F-actin is a hyponym of actin; that is, F-actin is a word with a more specific, narrower meaning than actin:

actin: one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form
F-actin: a filamentous form of actin.

actin (noun)	F-actin (noun)
one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form	a filamentous form of actin.