speech vs lecture

speech and lecture both are nouns.

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

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

As nouns, speech and lecture are synonyms defined as:

Other synonyms of speech include talking to.

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

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