Mute _h_ between vowels is disregarded and does not prevent
diphthongization, e.g. _a^h^ora_, _re^h^usar_.
The separation of two vowels that are usually united in one syllable
is called _diaeresis_, e.g. _vi|oleta_.
The union in one syllable of two vowels that are usually in separate
syllables is called _synaeresis_, e.g. _ca^os_.