The difference between Discourse and Sermon

When used as nouns, discourse means verbal exchange, conversation, whereas sermon means religious discourse.

When used as verbs, discourse means to engage in discussion or conversation, whereas sermon means to discourse to or of, as in a sermon.

check bellow for the other definitions of Discourse and Sermon

Discourse as a noun (uncountable, archaic):

Verbal exchange, conversation.
Discourse as a noun (uncountable):

Expression in words, either speech or writing.
Discourse as a noun (countable):

A formal lengthy exposition of some subject, either spoken or written.

Examples:

"The preacher gave us a long discourse on duty."
Discourse as a noun (countable):

Any rational expression, reason.
Discourse as a noun (social sciences, countable):

An institutionalized way of thinking, a social boundary defining what can be said about a specific topic (after Michel Foucault).
Discourse as a noun (obsolete):

Dealing; transaction.

Discourse as a verb (intransitive):

To engage in discussion or conversation; to converse.
Discourse as a verb (intransitive):

To write or speak formally and at length.
Discourse as a verb (obsolete, transitive):

To debate.
Discourse as a verb:

To exercise reason; to employ the mind in judging and inferring; to reason.

Examples:

"rfquotek Dryden"
Discourse as a verb (obsolete, transitive):

To produce or emit (musical sounds).

Sermon as a noun:

Religious discourse; a written or spoken address on a religious or moral matter.
Sermon as a noun:

A lengthy speech of reproval.

Sermon as a verb (poetic, obsolete):

To discourse to or of, as in a sermon.

Examples:

"rfquotek Spenser"
Sermon as a verb (poetic, obsolete):

To tutor; to lecture.