vox vs voice over

vox and voice over both are nouns.

Word	Noun	Adjective	Verb	Adverb
vox	Yes	No	No	No
voice over	Yes	No	No	No

As nouns, voice over is a hyponym of vox; that is, voice over is a word with a more specific, narrower meaning than vox:

vox: the sound made by the vibration of vocal folds modified by the resonance of the vocal tract
voice over: the voice on an unseen commentator in a film of television program

Other hyponyms of vox include singing voice, sprechgesang, sprechstimme, voice.

vox (noun)	voice over (noun)
the sound made by the vibration of vocal folds modified by the resonance of the vocal tract	the voice on an unseen commentator in a film of television program