Hiatus is most frequently found between words having a close
syntactical relation, particularly if the initial vowel of the second
word is in a constituent syllable. It may occur between the article
and its substantive, the possessive adjective and its substantive, a
preposition and its object, the negatives _no_ and _ni_ and a
following vowel; and after the conjunctions _y, que, si_, and other
words having a weak accent such as _desde, coma, todo, otro, cuando_,
etc.
Hiatus is most likely to occur when the accented vowel is the initial
vowel of the final word in a phrase or verse, or of a word that has a
strongly accented position in the verse; as, for example, when the
syllable is the next to the last syllable in a verse, or is the fourth
or eighth syllable of a hendecasyllabic verse of the second class.
Ex. _Rumor de besos y batir de alas_, p. 168, X, l. 6.
Ex. _Como la ola que á la playa viene_, p. 178, XXXVII, l. 19.
In the above-mentioned case, the phrase _de^oro_ is usually joined by
synalepha.
Ex. _Mi frente es pálida, mis trenzas de^oro._ Becquer.
Hiatus is, however, sometimes observed in this phrase.
Ex. _De plumas y de oro_, p. 180, XL, l. 28.
When both vowels are accented hiatus is more common than synalepha,
even though there is no close syntactical relation, although the
vowels may be joined by synalepha if they do not come in a constituent
syllable.