extemporization vs improvisation

extemporization and improvisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
extemporization	Yes	No	No	No
improvisation	Yes	No	No	No

As nouns, extemporization and improvisation are synonyms defined as:

extemporization and improvisation: a performance given extempore without planning or preparation

Other synonyms of extemporization include extemporisation.

extemporization (noun)	improvisation (noun)
a performance given extempore without planning or preparation	an unplanned expedient
	a performance given extempore without planning or preparation
	a creation spoken or written or composed extemporaneously (without prior preparation)