speech vs inflection

speech and inflection both are nouns.

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

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

Other hyponyms of speech include address, catch, tongue, shibboleth, tone, tone of voice, elocution, prosody, modulation.

speech (noun)	inflection (noun)
the mental faculty or power of vocal communication	the patterns of stress and intonation in a language
(language) communication by word of mouth	a manner of speaking in which the loudness or pitch or tone of the voice is modified
the act of delivering a formal spoken communication to an audience	deviation from a straight or normal course
words making up the dialogue of a play	a change in the form of a word (usually by adding a suffix) to indicate a change in its grammatical function
a lengthy rebuke
the exchange of spoken words
your characteristic style or manner of expressing yourself orally
something spoken