central vowel vs vowel

central vowel and vowel both are nouns.

Word	Noun	Adjective	Verb	Adverb
central vowel	Yes	No	No	No
vowel	Yes	No	No	No

As nouns, vowel is a hypernym of central vowel; that is, vowel is a word with a broader meaning than central vowel:

central vowel: (linguistics) any vowel sound in which the tongue is positioned halfway between a front vowel and a back vowel.
vowel: a speech sound made with the vocal tract open

Other hypernyms of central vowel include vowel sound.

central vowel (noun)	vowel (noun)
(linguistics) any vowel sound in which the tongue is positioned halfway between a front vowel and a back vowel.	a speech sound made with the vocal tract open
	a letter of the alphabet standing for a spoken vowel