ruck vs flexure

ruck and flexure both are nouns.

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

As nouns, flexure is a hypernym of ruck; that is, flexure is a word with a broader meaning than ruck:

Other hypernyms of ruck include bend, crease, crimp, fold, plication.

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

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