expatiation vs expansion

expatiation and expansion both are nouns.

Word	Noun	Adjective	Verb	Adverb
expatiation	Yes	No	No	No
expansion	Yes	No	No	No

As nouns, expansion is a hypernym of expatiation; that is, expansion is a word with a broader meaning than expatiation:

expatiation: a discussion (spoken or written) that enlarges on a topic or theme at length or in detail
expansion: a discussion that provides additional information

Other hypernyms of expatiation include elaboration, enlargement.

expatiation (noun)	expansion (noun)
a discussion (spoken or written) that enlarges on a topic or theme at length or in detail	the act of increasing (something) in size or volume or quantity or scope
	adding information or detail
	a discussion that provides additional information
	a function expressed as a sum or product of terms