When the vowels from the accented syllable to the end of the word are
the same, but the consonants are different, the rhyme is called
assonance. Therefore, _inflaman_ and _pasa_ assonate in á-a; _negros_
and _creo_ in e-o.
In words accented on the last syllable (_agudas_), the assonance is
that of the last syllable only, e.g. _perdón--espiró_; _azul--tú_.
In words accented on the antepenult (_esdrújulas_) or on a preceding
syllable, only the accented syllable and the final syllable count for
purposes of assonance. Therefore, _fábula_ and _lágrimas_ assonate in
á-a; _trémulo_ and _vértigo_ assonate in é-o.
Words accented on the last syllable (_agudas_) cannot assonate with
words accented on the penult (_llanas_), or with those accented on the
antepenult (_esdrújulas_) or upon any preceding syllable.
In words _llanas_ or _esdrújulas_ the assonance is of two vowels only.
In diphthongs the accented vowel only is considered if the diphthong
occur in an accented syllable. Therefore, _verte_ and _duermes_
assonate in e-e; _baile_ and _parte_ assonate in a-e.
Words _llanas_ may assonate with words accented on the antepenult
(_esdrújulas_). Therefore, _pórtico_ and _olmos_ assonate in ó-o.
For purposes of assonance little use is made of words accented on a
syllable preceding the antepenult.
In a final accented or unaccented syllable u and i are absorbed, for
purposes of assonance, by a preceding or following a, o, or e.
Therefore, _sabia_ and _gratia_ assonate in á-a; _igual_ and _mar_
assonate in a, _pleita_ and _pliega_ assonate in é-a.
If in assonance a weak vowel is united in a diphthong with a strong
vowel, the assonance is called _compound assonance_, e.g.
_guarda--fatua_.
Assonance between two single vowels is called _simple assonance_, e.g.
_sangre--trae_.
This distinction is of little value, however, for verses in simple and
compound assonance alternate constantly.
In the case of two strong vowels forming a diphthong after an accented
syllable, the following rules apply.
a in a final unaccented syllable predominates over a preceding or
succeeding o in the same syllable. Therefore, _Astárloa_ and _Dánao_
assonate in á-a.
a in a final unaccented syllable predominates over a preceding or
following e in the same syllable. Therefore, _corpórea_ and _rósea_
assonate in ó-a.
o in a final unaccented syllable predominates over a preceding e in
the same syllable. Therefore, _óleo_ and _erróneo_ assonate in ó-o;
but o in a final unaccented syllable is dominated by a following e in
the same syllable, and the e counts in the assonance. Therefore,
_héroe_ and _veces_ assonate in é-e.
When two weak vowels (i, u) are united in a diphthong, the second
predominates. Thus _triunfo_ and _chulo_ assonate in ú-o; _cuido_ and
_bendito_ assonate in i-o.
There are twenty possible assonances in Spanish: á, ó, é, i, ú, á-a,
á-e, á-o, é-a, é-e, é-o, ó-a, ó-e, ó-o, i-a, i-e, i-o, ú-a, ú-e, ú-o.
Words that have in the final unaccented syllable i or u, not in
diphthongs, are considered for purposes of assonance as if ending in e
or o respectively. Therefore, _fácil_ and _nave_ assonate in á-e;
_espíritu_ and _líquido_, in i-o.
If ai occurs in a syllable after an a in the accented syllable, the i
rather than the a of the diphthong counts in the assonance. Therefore,
_cantares_ and _trocabais_ assonate in á-e. If the accented vowel is
not a, the a of ai counts in the assonance. Therefore, _Vicenta_ and
_quisierais_ assonate in é-a.
Consonantal rhyme should not be introduced in compositions written in
assonance. This rule is not always observed (see pp. 183-184, LIII).
The assonance of alternate lines (the even numbers) is the rule in
modern Spanish. If the composition is short the same assonance may be
kept throughout.
Blank Verse.--Verses which lack both consonantal rhyme and assonance
occur in Spanish, and are called _versos sueltos_ (or _libres_).
Compositions in blank verse are, however, extremely difficult to write
in Spanish, and are therefore comparatively rare.