vocal organ vs glottis

vocal organ and glottis both are nouns.

Word	Noun	Adjective	Verb	Adverb
vocal organ	Yes	No	No	No
glottis	Yes	No	No	No

As nouns, glottis is a hyponym of vocal organ; that is, glottis is a word with a more specific, narrower meaning than vocal organ:

vocal organ: any of the organs involved in speech production
glottis: the vocal apparatus of the larynx; the true vocal folds and the space between them where the voice tone is generated

Other hyponyms of vocal organ include articulator, larynx, voice box.

vocal organ (noun)	glottis (noun)
any of the organs involved in speech production	the vocal apparatus of the larynx; the true vocal folds and the space between them where the voice tone is generated