lecture vs sermon

lecture and sermon both are nouns.

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

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

Other hyponyms of lecture include preaching, curtain lecture.

lecture (noun)	sermon (noun)
teaching by giving a discourse on some subject (typically to a class)	an address of a religious nature (usually delivered during a church service)
a speech that is open to the public	a moralistic rebuke
a lengthy rebuke

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