un ci^elo_, p. 172, XXIII, l. 2. [Diphthong.]

Ex. _Domando el rebelde, mezquino idi|oma_, p. 164, I, l. 6. [No
diphthong.]

Diaeresis or synaeresis may usually be employed according to the case.

Thus, _fiel_ becomes by diaeresis _fi|el_, and _br|ioso_ becomes by
synaeresis _bri^oso_.

It should be remembered that in some words the accentuation is
variable, while in others it is fixed.

There are two classes of words that have a variable accentuation:
first, those in which an unaccented weak vowel is followed by an
accented strong vowel, e.g. _majestu^oso_, _majestu|oso_; second,
those in which an accented strong vowel is followed by an unaccented
strong vowel, e.g. _tra|e, tra^e._

Ex. _Cre^es que la afe|an_. Becquer.
_Cre|es que suspirando pasa el viento_, p. 171, XVI, l. 3.

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

ie and ue, derived from the Latin e and o respectively, form
indissoluble diphthongs.

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

Synaeresis may be employed to unite in a single syllable two
contiguous vowels (unaccented weak + accented strong) that are
separated on account of etymology, or, in the case of derivatives,
analogy with the original word; but diaeresis is employed very rarely
to dissolve a proper diphthongal combination (unaccented weak +
accented strong).

For example, _di|ario_ by analogy with _dia_, and _fi|o_ from the
Latin _fidavit_, have ordinarily the _i_ in separate syllables, but a
diphthong may be formed by synaeresis.

(3) _When the two contiguous vowels are weak_.

(a) Two contiguous weak vowels with the accent on the first form an
indissoluble diphthong, e.g. _mu^y_.

(b) Two contiguous weak vowels with the accent on the second may or
may not form a diphthong.

Ex. _Si antes no juras que por ru^in falsia_. Hermosilla.
[Diphthong.]

Ex. _Con sus mil rue|idos_, p. 188, LXXIII, l. 19, [No diphthong.]

c. Two contiguous vowels after the accented syllable.

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

Ex. _Tu, sombra aere^a que, cuantas veces_, p. 170, XV, l. 7.

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.

(3) If a weak vowel is foll