VERBS WHOSE STEMS END IN LL OR Ñ
This type drops the i of the diphthong, in all the forms whose endings begin with ie or ió. This loss does not affect the pronunciation of the verb because the palatal ll and ñ of the stem "absorbs" the i. Compare English million and Spanish millón or English canyon and Spanish cañón.
43. Bullir, to boil.
Gerundio: bullendo.
Pretérito: bulló (tercera persona, singular), bulleron (plural).
Imperfecto de Subjuntivo: bullese, etc.; bullera, etc.
Futuro de Subjuntivo: bullere, etc.
44. Bruñir, to burnish.
Gerundio: bruñendo.
Pretérito: bruñó (tercera persona, singular), bruñeron (plural).
Imperfecto de Subjuntivo: bruñese, etc.; bruñera, etc.
Futuro de Subjuntivo: bruñere, etc.
VERBS HAVING UNACCENTED I BETWEEN TWO VOWELS
Since unaccented i may not stand between two vowels, those verbs of the second and third conjugation whose stems end in a vowel, substitute a y for the i. Thus the form creiendo is avoided and creyendo is written. These changes occur in the present participle, the preterite, third singular and plural, the imperfect subjunctive and the future subjunctive. Creer and huir will serve to illustrate this point.
45. Creer, to believe.
Gerundio: creyendo.
Pretérito: creyó; creyeron.
Imperfecto de Subjuntivo: creyese, etc.; creyera, etc.
Futuro de Subjuntivo: creyere, etc.
46. Huir, to flee.
In verbs ending in uir, where the u is pronounced, a y is inserted whenever u would come before a, e, or o. Furthermore, unstressed i changes as in 45.
Gerundio: huyendo.
Presente de Indicativo: huyo, huyes, huye, huimos, huís, huyen.
Presente de Subjuntivo: huya, huyas, huya, huyamos, huyáis, huyan.
Pretérito: huí, huiste, huyó, huimos, huisteis, huyeron.
Imperfecto de Subjuntivo: huyese, etc.; huyera, etc.
Futuro de Subjuntivo: huyere, etc.
Imperativo: huye, huid.