A problem of importance is to determine, when two or more vowels come together, whether they form one syllable or more. The vowels are either strong (a, e, o) or weak (i, y, u), and they come together under three chief conditions; viz., ([I]) the accent of the word may be on one of the contiguous vowels; ([II]) it may be on a preceding syllable; ([III]) it may be on a syllable following them.
I. Combinations of Two Vowels, one of which is Accented
(1) If one of two strong vowels (a, e, o) coming together has the accent, they do not form a diphthong, and therefore do not count as a single syllable in the verse. Dissyllables, for example, are Jaén, nao, leal, león; trisyllables are azahar (h mute), creemos, canoa.
Exceptionally, the two strong vowels are contracted: e.g., Samaniego has contracted them in the hendecasyllable,
El león, rey de los bosques poderoso,
and Espronceda in a tetrasyllable,
Y no hay playa
Sea cualquiera, etc.
This contraction, called synæresis, is less harsh when the unaccented vowel is e. It is frequent, however, with the first two vowels of ahora.
(2) If two vowels come together, the first strong (a, e, o) and the second weak (i, y, u), and if the accent rests on the strong vowel, they regularly form a diphthong and count as one syllable; e.g., cauto, peine, feudo, convoy, rey, soy. The dissolution of this diphthong constitutes a very violent poetical license. When it occurs it is termed diæresis and is sometimes marked by the dots so called; e.g., glorïoso, suäve.