If two contiguous vowels of a single word are pronounced in but one syllable they form a diphthong, e.g. hu^esped.

In Bo^abdíl, if a were not dominant, the diphthong would be dissolved.

Habrá po^esta, p. 165, IV, l. 4. (a) Diaeresis may be employed to dissolve the diphthong.

(a) There is no diphthong if one of two contiguous strong vowels receives the accent.

For example, loa would shift the accent from o to a in order to form a diphthong.

(a) There is no diphthong if an accented weak vowel precedes a strong.

(c) If an accented strong vowel precedes a weak, they form a diphthong.

The diphthong is rarely dissolved, and is usually marked with a diaresis, if dissolution takes place.

Beso del aura, onda de luz, p. 170, XV, l. 5. (d) If an accented strong vowel follows a weak they may or may not form a diphthong.

[Diphthong.] Ex.

[No diphthong.]

Etymological conditions often determine whether or not a diphthong is formed.

The ending -ión for substantives is usually a diphthong and rarely suffers dissolution.

[Diphthong.] Ex.

Con sus mil rü|idos, p. 188, LXXIII, l. 19, [No diphthong.]

(1) Two contiguous strong vowels after the accented syllable naturally form a diphthong.

Diaeresis may be employed to dissolve the diphthong.

(2) If a strong vowel is followed by a weak vowel after the accented syllable, they form a diphthong, e.g. hablaba^is, amara^is.

This diphthong is easily dissolved.

The diphthong may, however, be dissolved, e.g. estatu|a, tenu|e, nadi|e.

In the following cases the groups of vowels which would usually make triphthongal synalepha are pronounced in two syllables: (1) When the first word of the group ends in two vowels which do not form a diphthong.

Mientras la cencia á descubrir no alcance, p. 165, IV, l. 13. (4) When the first word ends in a single vowel, and the second word begins with a diphthong in a constituent syllable.

If in assonance a weak vowel is united in a diphthong with a strong vowel, the assonance is called compound assonance, e.g. guardafatua.

In the case of two strong vowels forming a diphthong after an accented syllable, the following rules apply.

Therefore, héroe and veces assonate in é-e. When two weak vowels (i, u) are united in a diphthong, the second predominates.