bend vs twirl

bend and twirl both are nouns.

Word	Noun	Adjective	Verb	Adverb
bend	Yes	No	Yes	No
twirl	Yes	No	Yes	No

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

bend: an angular or rounded shape made by folding
twirl: a sharp bend in a line produced when a line having a loop is pulled tight

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

bend (noun)	twirl (noun)
curved segment (of a road or river or railroad track etc.)	the act of rotating rapidly
diagonal line traversing a shield from the upper right corner to the lower left	a sharp bend in a line produced when a line having a loop is pulled tight
movement that causes the formation of a curve
an angular or rounded shape made by folding
a circular segment of a curve

bend (verb)	twirl (verb)
cause (an object) to assume a crooked or angular form	turn in a twisting or spinning motion
bend a joint	cause to spin
form a curve
change direction
turn from a straight course, fixed direction, or line of interest
bend one's back forward from the waist on down