vocalize vs speak

vocalize and speak both are verbs.

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

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

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

vocalize (verb)	speak (verb)
pronounce as a vowel	express in speech
express or state clearly	exchange thoughts; talk with
utter with vibrating vocal chords	use language
utter speech sounds	give a speech to
sing (each note a scale or in a melody) with the same vowel	make a characteristic or natural sound