improvisation vs expedient

improvisation and expedient both are nouns.

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

As nouns, expedient is a hypernym of improvisation; that is, expedient is a word with a broader meaning than improvisation:

improvisation (noun)	expedient (noun)
an unplanned expedient	a means to an end; not necessarily a principled or ethical one
a performance given extempore without planning or preparation
a creation spoken or written or composed extemporaneously (without prior preparation)

improvisation (adjective)	expedient (adjective)
	serving to promote your interest
	appropriate to a purpose; practical