preaching vs sermon

preaching and sermon both are nouns.

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

As nouns, preaching and sermon are synonyms defined as:

preaching and sermon: an address of a religious nature (usually delivered during a church service)

Other synonyms of preaching include discourse.

As nouns, preaching and sermon are synonyms defined as:

preaching (noun)	sermon (noun)
an address of a religious nature (usually delivered during a church service)	an address of a religious nature (usually delivered during a church service)
a moralistic rebuke	a moralistic rebuke