protraction vs lengthening

protraction and lengthening both are nouns.

Word	Noun	Adjective	Verb	Adverb
protraction	Yes	No	No	No
lengthening	Yes	No	No	No

As nouns, protraction and lengthening are synonyms defined as:

Other synonyms of protraction include perpetuation, prolongation.

protraction (noun)	lengthening (noun)
the act of prolonging something	the act of prolonging something
the consequence of being lengthened in duration