talk about vs talk

talk about is not a noun while talk is a noun.

Word	Noun	Adjective	Verb	Adverb
talk about	No	No	Yes	No
talk	Yes	No	Yes	No

As verbs, talk is a hypernym of talk about; that is, talk is a word with a broader meaning than talk about:

Other hypernyms of talk about include mouth, speak, utter, verbalise, verbalize.

talk about (noun)	talk (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 about (verb)	talk (verb)
to consider or examine in speech or writing	express in speech
discuss or mention	exchange thoughts; talk with
	reveal information
	use language
	deliver a lecture or talk
	divulge confidential information or secrets