prolonged vs lengthy

prolonged and lengthy both are adjectives.

Word	Noun	Adjective	Verb	Adverb
prolonged	No	Yes	No	No
lengthy	No	Yes	No	No

As adjectives, prolonged and lengthy are synonyms defined as:

prolonged and lengthy: relatively long in duration; tediously protracted

Other synonyms of prolonged include drawn-out, extended, protracted.

prolonged (adjective)	lengthy (adjective)
drawn out or made longer spatially	relatively long in duration; tediously protracted
relatively long in duration; tediously protracted