straighten vs bend

straighten is not a noun while bend is a noun.

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

straighten (noun)	bend (noun)
	curved segment (of a road or river or railroad track etc.)
	diagonal line traversing a shield from the upper right corner to the lower left
	movement that causes the formation of a curve
	an angular or rounded shape made by folding
	a circular segment of a curve

straighten (verb)	bend (verb)
put (things or places) in order	cause (an object) to assume a crooked or angular form
make straight or straighter	bend a joint
make straight	form a curve
straighten by unrolling	change direction
straighten up or out; make straight	turn from a straight course, fixed direction, or line of interest
get up from a sitting or slouching position	bend one's back forward from the waist on down