# Diphthongs: one syllable, two vowels

> id: pronunciation.diphthongs · category: pronunciation · depth: standard · levels: A2 · review: internally_reviewed

**Summary.** Weak (i, u) + strong (a, e, o) or weak + weak fuse into one syllable: bien, bueno, ciudad, aire. Strong + strong stay separate: le-er, ca-os.

Fourteen combos glide: ia ie io ua ue uo (rising: tierra, fuego), ai ei oi au eu ou (falling: aire, deuda), iu ui (ciudad, cuidado). They count as ONE syllable for stress rules.

An accent on the weak vowel breaks the diphthong into two syllables — that's hiatus (día, país) — see the hiatus rule.

Why this matters mechanically: a diphthong counts as a single syllable for the stress rules, so vie-ne and bue-no are two syllables, not three. The fusion only breaks when a written accent lands on the weak vowel (i or u) — that is hiatus, and it is exactly what the tilde in día or país is signalling.

## Examples
- Bueno, hay tiempo el miércoles. — Well, there's time on Wednesday. *(ue, ai, ie, ié: all one syllable.)*
- Europa y Asia. — Europe and Asia.
- Bueno y tierra tienen diptongo; día y país, no. — 'Bueno' and 'tierra' have a diphthong; 'día' and 'país' don't.

Related: pronunciation.hiatus, pronunciation.syllabification

License: CC BY-SA 4.0 — Spanish Rules Library — spanishruleslibrary.com