discourse vs chat

discourse and chat both are nouns.

Word	Noun	Adjective	Verb	Adverb
discourse	Yes	No	Yes	No
chat	Yes	No	Yes	No

As verbs, chat is a hyponym of discourse; that is, chat is a word with a more specific, narrower meaning than discourse:

discourse (noun)	chat (noun)
an extended communication (often interactive) dealing with some particular topic	songbirds having a chattering call
extended verbal expression in speech or writing	birds having a chattering call
an address of a religious nature (usually delivered during a church service)	an informal conversation

discourse (verb)	chat (verb)
talk at length and formally about a topic	talk socially without exchanging too much information
carry on a conversation
to consider or examine in speech or writing