Vowel sounds such as [e, o] produced with the tongue around the midpoint on the vertical axis. Sometimes languages have two mid vowels, like [e] and [ε]. In such a case the former vowel is referred to as upper-mid (or 'half-close' or 'close-mid') and the latter vowel is referred to as lower-mid (or 'half-open' or 'open-mid'). See also high, low, front, central, back.