lengthened vs extended

lengthened and extended both are adjectives.

Word	Noun	Adjective	Verb	Adverb
lengthened	No	Yes	No	No
extended	No	Yes	No	No

As adjectives, lengthened and extended are synonyms defined as:

Other synonyms of lengthened include elongated, prolonged.

lengthened (adjective)	extended (adjective)
drawn out or made longer spatially	fully extended or stretched forth
	beyond the literal or primary sense
	large in spatial extent or range or scope or quantity
	drawn out or made longer spatially
	relatively long in duration; tediously protracted