Spanish Vowel Hiatus

Quick Answer

A Spanish word may contain a combination of two vowels. When each of those two vowels belongs to a different syllable, it's called an hiato(hiatus).

For example, the word caer(to fall) has two syllables: ca- and -er. Its vowels (a and e) form a hiatus because they belong to different syllables.

An hiato shouldn’t be confused with a diptongo(diphthong), which is also a combination of two vowels in the same syllable.

Spanish Hiatuses

What Are They and Why Are They Important?

A hiatus is a sequence of two vowels that belong to different syllables and are normally pronounced separately. For example caída(fall), tarea(homework), or cooperar(to cooperate).
There are three types of hiatus in Spanish:
- A stressed weak vowel (i or u) plus an unstressed strong vowel (a, e, or o). For example: María(Maria), púa(sharp point, pick), transeúnte(passerby, pedestrian).
- Two strong vowels together. For example: héroe(hero), caer(to fall), anchoa(anchovy).
- The same two vowels together. For example: leer(to read), zoo(zoo), Abraham(Abraham).
Apart from their pronunciation, hiatuses are important because they determine the number and nature of the syllables of a word, which in turn will many times determine whether that word is written with or without an accent, called tildein Spanish. Let's check out the pronunciation of some common hiatuses!

Remember that the h is silent in Spanish, so it does not make any sound in words such as Abraham in the examples above, or other words of the same type, like azahar(orange/lemon blossom) or alcohol(alcohol). Therefore, these combinations are still hiatuses.

Spanish Hiatus Pronunciation

Below are examples of Spanish hiatuses and their pronunciation.

Hiatus	Pronunciation	Example
aí	ah - EE	país, ahí
aú	ah - OO	Raúl, ataúd
oí	oh - EE	oír, mohín
eí	eh - EE	reír, vehículo
eú	eh - OO	transeúnte, reúma
ía	EE - ah	día, María
íe	EE - eh	ríe, sonríe
ío	EE - oh	río, brío
úa	OO - ah	cacatúa, capicúa
úe	OO - eh	acentúe, actúe
úo	OO - oh	continúo, búho
ae	ah - eh	caer, faena
ao	ah - oh	aorta, ahora
aa	ah - ah	azahar, portaaviones
ea	eh - ah	leal, quehacer
eo	eh - oh	leo, rehogar
ee	eh - eh	poseer, dehesa
oa	oh - ah	coágulo, almohada
oe	oh - eh	poetisa, bohemio
oo	oh - oh	zoológico, alcohol

Spanish Hiatus Accentuation

Written accents are called tildes in Spanish. Here are a few tips to know when to place written accents on words that contain hiatuses.

Tips for Writing Accents on Hiatuses

Tip	Examples
Always accent combinations of a stressed weak vowel and an unstressed strong vowel.	caída(fall), hindúes(Hindus)
Always accent words stressed on the last syllable that end in n, s, or a vowel (excluding y).	Noé(Noah), acordeón(accordion), rehén(hostage)
Always accent words stressed on the penultimate syllable that end in a consonant other than n or s (including y).	bóer(Boer), Sáenz(Saenz, a common surname)
Always accent words stressed on the third-to-last syllable.	océano(ocean), poético(poetic)

Accents and Weak/Strong Vowels

Note that words containing hiatuses follow the usual Spanish written accent rules, but there is an exception to those rules outlined at the top of the previous table for combinations of a stressed weak vowel and an unstressed strong vowel, which take a tilde no matter which syllable they are in.

Funny Thing Is...

...the word hiato itself contains a diptongo, i.e., a combination of vowels that are normally pronounced in the same syllable. It has two syllables, hia- and -to, so the vowels ia form a diphthong, not a hiatus!

So, Whatever Happened to the Accent On Guion?

The word guion(script, hyphen) used to have a tilde on the letter o. It was perceived as having two syllables (the vowels io would form a hiatus) and, according to Spanish rules for words ending in n or s, required an accent on the final syllable (e.g., guión). However, many Spanish native speakers, particularly those in Latin America, actually pronounce this word as a monosílabo(monosyllable). In general, Spanish monosyllabic words aren’t accented, so there was discussion about whether guion and similar words should or should not bear a written accent. Finally, it was decided that they should be considered monosyllabic for spelling purposes (pronunciation is a free country), so words like guion and truhan(rogue) lost their tildes. The decision was controversial and, to this day, some well-known authors and many other native speakers refuse to use the unaccented form.