univocal

Earliest known print evidence of univocal, in the sense of "having one meaning only," dates the word to the mid-1500s, somewhat earlier than its more familiar antonym equivocal (meaning "often misleadingly subject to two or more interpretations"). Both words trace back to the Latin noun vox, which means "voice." The prefix uni- ("one") was combined with vox to create the Late Latin word univocus, from which English speakers borrowed univocal. Univocal was indeed once used in the sense of "speaking in one voice" (or "unanimous") as its etymology would imply, but that use is now obsolete.