talk vs hold forth

talk is a noun but hold forth is not a noun.

Word	Noun	Adjective	Verb	Adverb
talk	Yes	No	Yes	No
hold forth	No	No	Yes	No

As verbs, hold forth is a hyponym of talk; that is, hold forth is a word with a more specific, narrower meaning than talk:

talk (noun)	hold forth (noun)
the act of giving a talk to an audience
an exchange of ideas via conversation
idle gossip or rumor
a speech that is open to the public
discussion; (`talk about' is a less formal alternative for `discussion of')

talk (verb)	hold forth (verb)
express in speech	talk at length and formally about a topic
exchange thoughts; talk with
reveal information
use language
deliver a lecture or talk
divulge confidential information or secrets