In phonetics/phonology, a vowel is a speech sound in whose articulation the oral part of the breath channel is not constricted enough to cause audible friction.
A relational adjective from vowel that is occasionally used is vocalic.
Speech sounds with audible constriction are called consonants; sounds intermediate between vowels and consonants are called semi-vowels (not "semi-consonants").
The word goes back to French voyelle, from Latin (littera) vocalis 'voice letter' (from vox 'voice').
French voyelle German Vokal