oa, oe, as in loa, praise; poema, poem.
DIPHTHONGS.
These are formed by combining one of the strong vowels, a, e, o, with one of the weak vowels, i, u, or by a combination of the two weak vowels alone. In the former the stress falls on the strong vowel, and in the latter on the second;
ai (ay), au, as in aire, air; causa, cause;
ei (ey), eu, as in seis, six; neutro, neuter;
ia, ie, io, iu, as in diario, daily; viuda, widow;
oi (oy), ou, as in boina, cap; bou, fishing-boat;
ua, ue, ui (uy), uo, as in agua, water; ruido, noise.
TRIPHTHONGS.
These are a combination of the two weak vowels with one of the strong ones: