flexure vs ruck

flexure and ruck both are nouns.

Word	Noun	Adjective	Verb	Adverb
flexure	Yes	No	No	No
ruck	Yes	No	Yes	No

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

Other hyponyms of flexure include plait, pleat, kink, twirl, twist, pucker, accordion fold, concertina fold, z-fold, zig-zag fold.

flexure (noun)	ruck (noun)
act of bending a joint; especially a joint between the bones of a limb so that the angle between them is decreased	a crowd especially of ordinary or undistinguished persons or things
an angular or rounded shape made by folding	an irregular fold in an otherwise even surface (as in cloth)
the state of being flexed (as of a joint)

flexure (verb)	ruck (verb)
	become wrinkled or drawn together