lecture vs speech

lecture and speech both are nouns.

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

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

Other hypernyms of lecture include address.

As nouns, lecture and speech are synonyms defined as:

Other synonyms of lecture include talking to.

lecture (noun)	speech (noun)
teaching by giving a discourse on some subject (typically to a class)	the mental faculty or power of vocal communication
a speech that is open to the public	(language) communication by word of mouth
a lengthy rebuke	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

lecture (verb)	speech (verb)
censure severely or angrily
deliver a lecture or talk