fillet vs filet mignon

fillet and filet mignon both are nouns.

Word	Noun	Adjective	Verb	Adverb
fillet	Yes	No	Yes	No
filet mignon	Yes	No	No	No

As nouns, filet mignon is a hyponym of fillet; that is, filet mignon is a word with a more specific, narrower meaning than fillet:

Other hyponyms of fillet include Chateaubriand, tournedos.

fillet (noun)	filet mignon (noun)
a narrow headband or strip of ribbon worn as a headband	small steak cut from the thick end of a beef tenderloin
fastener consisting of a narrow strip of welded metal used to join steel members
lace having a square mesh
a bundle of sensory nerve fibers going to the thalamus
a boneless steak cut from the tenderloin of beef
a longitudinal slice or boned side of a fish

fillet (verb)	filet mignon (verb)
cut into filets
decorate with a lace of geometric designs