babble vs speak

babble is a noun but speak is not a noun.

Word	Noun	Adjective	Verb	Adverb
babble	Yes	No	Yes	No
speak	No	No	Yes	No

As verbs, speak is a hypernym of babble; that is, speak is a word with a broader meaning than babble:

babble: utter meaningless sounds, like a baby, or utter in an incoherent way
speak: express in speech

Other hypernyms of babble include mouth, talk, utter, verbalise, verbalize.

babble (noun)	speak (noun)
gibberish resembling the sounds of a baby

babble (verb)	speak (verb)
to talk foolishly	express in speech
divulge confidential information or secrets	exchange thoughts; talk with
utter meaningless sounds, like a baby, or utter in an incoherent way	use language
flow in an irregular current with a bubbling noise	give a speech to
	make a characteristic or natural sound