discussion vs dilation

discussion and dilation both are nouns.

Word	Noun	Adjective	Verb	Adverb
discussion	Yes	No	No	No
dilation	Yes	No	No	No

As nouns, dilation is a hyponym of discussion; that is, dilation is a word with a more specific, narrower meaning than discussion:

discussion: an extended communication (often interactive) dealing with some particular topic
dilation: a lengthy discussion (spoken or written) on a particular topic

Other hyponyms of discussion include detail, consideration, talk, elaboration, enlargement, expansion.

discussion (noun)	dilation (noun)
an exchange of views on some topic	the act of expanding an aperture
an extended communication (often interactive) dealing with some particular topic	a lengthy discussion (spoken or written) on a particular topic