discussion vs speech

discussion and speech both are nouns.

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

As nouns, speech is a hypernym of discussion; that is, speech is a word with a broader meaning than discussion:

discussion (noun)	speech (noun)
an exchange of views on some topic	the mental faculty or power of vocal communication
an extended communication (often interactive) dealing with some particular topic	(language) communication by word of mouth
	the act of delivering a formal spoken communication to an audience
	words making up the dialogue of a play
	a lengthy rebuke
	the exchange of spoken words
	your characteristic style or manner of expressing yourself orally
	something spoken