Pronunciation: accents on diphthongs

A diphthong occurs when two vowels are in the same syllable and are pronounced together.

Strong and Weak Vowels

Spanish vowels are defined as strong or weak:

  • strong vowels: a / e / o
  • weak vowels: i / u

For two vowels to be part of the same syllable, the vowel combination must be one of the following:

weak + weak (i, u + i, u)

Luisa, construir, ciudad, triunfarLuisa, to build, city, to triumph

weak + strong (i, u + a, e, o)

hielo, miedo, guapaice, fear, pretty

strong + weak (a, e, o + i, u)

deuda, aumento, Moisésdebt, rise, Moses

Any other combination of vowels means that the vowels are in separate syllables, see Pronunciation: accents on hiatuses.

How do we accentuate these words if the stress falls on the diphthong?

All words containing diphthongs follow the general rules for accentuation. If the stress is on the syllable with the diphthong, these are the rules:

1. If the combination is weak + weak, we stress the second weak vowel. For example:

cdala.look after her.

cuí-da-la (3 syllables)

2. If the combination is strong + weak or weak + strong, we always stress the strong vowel (a, e, o). For example:

desps.after, later.

des-pués (2 syllables)

tambnalso

tam-bién (2 syllables)

See also Pronunciation: Where to stress a word in Spanish

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Examples and resources

hielo, miedo, guapaice, fear, pretty
cdala.look after her.
Luisa, construir, ciudad, triunfarLuisa, to build, city, to triumph
desps.after, later.
tambnalso
deuda, aumento, Moisésdebt, rise, Moses
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