lengthening vs protraction

lengthening and protraction both are nouns.

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

As nouns, lengthening and protraction are synonyms defined as:

Other synonyms of lengthening include perpetuation, prolongation.

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