speech vs utterance

speech and utterance both are nouns.

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

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

Other hypernyms of speech include vocalization.

speech (noun)	utterance (noun)
the mental faculty or power of vocal communication	the use of uttered sounds for auditory communication
(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