Spanish Diphthongs & Triphthongs – When to pronounce the vowels in the same syllable + Examples

Diphthong, triphthong, hiatus… These words sound complicated.

Why are they so important?

Why do you need to know how to recognize them? Actually, you don’t need it; unless you want to pronounce Spanish correctly, of course!

And I guess that’s why you’re here.

Before you continue reading I recommend you to take a look at this article on how to pronounce the Spanish vowels so that you squeeze the 100% of this post.

I’m going to make it as simple as possible so that you can easily understand how Spanish diphthongs and triphthongs work.

I didn’t want to make this post very thick, so I’ve divided it into 2 parts:

  1. Diphthongs and triphthongs (this post)
  2. Hiatuses (next post)

If you want to go straight to the point, click here.


Spanish diphthongs are quite different from English diphthongs so before telling you how to pronounce Spanish diphthongs, I will explain to you:

  • What’s a diphthong
  • 2 differences between English and Spanish diphthongs and
  • How to recognize Spanish diphthongs in 2 steps.

What is a diphthong

A diphthong is formed by two vowel sounds, which are pronounced within the same syllable.

For example:
In English, the word loan – it’s pronounced /ləʊn/. The 2 vowels are pronounced in the same syllable.
In Spanish, the word aire – it’s pronounced / The vowels A and I are pronounced in the same syllable.

More examples of Spanish diphthongs:
muela (
tenéis (
avión (
cuando (
veinte (
tienda (
puerta (

The 2 differences between English and Spanish diphthongs

  • Single yolk eggs.
    Difference between English and Spanish diphthongs when pronouncing them hiatus strong soft weak vowels

    Guess how many yolks there are inside these 2 eggs. One in each egg, right? So 2 eggs = 2 yolks.

    Good. That’s what happens with Spanish vowels: 1 vowel (egg) = 1 sound (yolk).
    Example: The words ir and mini. The letter I is always pronounced as one sound.

    However, sometimes you can find 2 yolks in one egg. Great! That can happen with English vowels as well. 1 vowel (egg) may have 1 or 2 sounds (yolks).
    Example: In the word king the letter I is pronounced as one sound but in the word ice the letter I is pronounced /aɪ/ (two sounds).

    In Spanish that would be impossible.

    You need 2 vowels to form a diphthong because 1 vowel = 1 sound. 

    Example: The word no.
    In English, it’s pronounced as a diphthong: /nəʊ/. Double yolk! (1 vowel = 2 sounds).
    In Spanish, this word could never be a diphthong because the vowel O is pronounced as it’s written: /no/ (1 vowel = 1 sound).

  • No empty eggs.
    empty sounds of Spanish vowels, diphthongs diptongos español vocales pronunciacion pronunciation how to pronounce guide step by step letters words syllables

    In English, the egg can be empty as well. No yolk inside.

    Example: The word good.
    It has two vowels, but they’re pronounced as one.

    In the Spanish language, there aren’t empty eggs. Every single egg has a yolk inside so all of the vowels are pronounced -except the letter U, in words with gue, gui, que, qui. But that’s another story and you already knew it.

In short, this is the difference between English and Spanish diphthongs:
Spanish diphthongs always have two (written) vowels -«gue», «gui», «que» and «qui» are an exception.
English vowels may be pronounced as two sounds (like in my), as one sound (like in yes) or may have no sound at all (like the letter E in little). In Spanish 1 vowel equals 1 sound.

How to recognize Spanish diphthongs in 2 steps

First step to know whether you have to pronounce the vowels in the same syllable: Recognize the vowels

To understand how diphthongs work you should know that there are two kinds of vowels -as you’ve already seen in the previous post (how to pronounce the Spanish vowels).

The space between your tongue and your palate will tell you what kind of vowel it is.

  • Open vowels: a, e, o.

They are called strong vowels as well because, in diphthongs and triphthongs, open vowels are pronounced stronger. To pronounce open vowels your tongue should be placed in the lower -or mid- part of your mouth.

Example: The word bien.
The diphthong is formed by the vowels i+e, but the emphasis is on the open vowel (e).

Spanish vowels position of the mouth to pronounce them open closed a e i o u for english speaker tongue diphthongs

  • Closed vowels: i, u.

They’re known as weak vowels too because, when there’s a diphthong or a triphthong, they are pronounced softer. You don’t need much room in your mouth to produce its sound so your tongue is placed close to the palate.

Examples: hacia, puerta.
The letters I and U are weaker. The letters A and E are the protagonists of the syllable.

If I say «ve hacia la puerta» -without pronouncing the closed or weak vowels-, people will understand more easily than if I only pronounce the closed vowels. In fact, this is the way babies speak when they say their first words. Instead of saying «bueno» they say «beno» and instead of «agua» they say «aba».

Let’s make it easier.

By reading the following story you’ll remember all this theory.

Story (part 1): Alberto doesn’t know that he lives with a mouse

The main characters of this story are Alberto, a strong elephant, and Milu, a weak and hungry mouse.

Their names aren’t a coincidence.
The elephant Alberto represents the open or strong vowels (a, e, o).
Milu, the mouse,  represents the closed or weak vowels (i, u).

Open and strong vowels a e o and Clsed and weak vowel i u pronounced in the same syllable or in different syllables

As you can see, Alberto is huge. He takes most of the attention and space -and food! He’s the king of the house (syllable) and doesn’t know that Milu is living with him.

Poor Milu, he’s weak and hungry -look at his teeth! He’s so weak that he can’t go very far. He wants to pursue his own path but he needs to stay close to Alberto, to eat his crumbs and get a bit of energy when Alberto doesn’t realize. But this energy isn’t enough. Milu needs urgently a big piece of cheese (accent mark).

closed vowels i u with tilde accent mark form hiatus hiato español

The open -or strong- vowel (Alberto) is the protagonist of the syllable so we pronounce it with more emphasis than the closed vowel (Milu).

Examples: pierna, piel
In both words, the open vowel (E) is pronounced stronger and the letter I sounds weaker:, piEl.

Remember that open vowels are the most important part of the syllable, but this doesn’t mean that they are the most important part of the word.

Example: cambio, cambió
The two words have the same diphthong (i+o) -in both cases, the letter O is pronounced with more emphasis than the letter I. However most important part of the word (accent) is different in the two words:, cam.BIÓ

But this isn’t the point of this post. If you want to read more on how to accent Spanish words, click on the link.

Story (part 2): Milu’s girlfriend

difference between diphthongs and hiatus in English and Spanish how to recognize, say and pronounce them.

Sometimes, when Alberto goes for a walk, Milu invites his girlfriend into Alberto’s home. But only sometimes -you’ll know why when you read the 4th part of the story. They are only two little mice so the two of them have plenty of space in the house.

That’s exactly what happens with Spanish diphthongs. One syllable can contain a máximum of 1 strong (open) vowel.

– Alberto (strong) = a, e, o.
– Milu (weak) = i, u.

Second step to know whether you have to pronounce the vowels in the same syllable: Answer this question

Now you know that Spanish diphthongs always have two written vowels (sometimes 3) and that you should identify them (open/closed) but how can you recognize that those 2 vowels should be pronounced in the same syllable?

Easy peasy.

All the Spanish diphthongs have, at least, one closed vowel without an accent mark (i, u). All of them. The other vowel can be any.


ciencia (cien.cia)
uedo (
iento (
uerpo (cuer.po)
eituna (

So this is the question:

«Is there 1 closed vowel without an accent mark (i, u)

If the answer is YES, then you have to pronounce those vowels in the same syllable.

On the following image, you can see how to form diphthongs and some examples with each combination. how to recognize composition vowels of Spanish diphthongs i u a e o examples pronounced strong weak letters

Spanish diphthongs are formed by (i/u) + (a/e/i/o/u):

  • 2 closed vowels (i/u)

(i + u) : Viuda, ciudad.
(u + i) : Fuimos, cuidado.

  • 1 open vowel (a/e/o) and 1 closed vowel (i/u)

(i/u) + (a/e/o) : Fiesta, camn, guapo.
(a/e/o) + (i/u) : Caimán, náufrago, Ceuta.

Beware of these letters

letters Spanish diphthongs explanation pronunciation how to avoid common mistakes and examples syllables together pronounced separated different

The letter H It doesn’t impede the formation of diphthongs Ahumado  (
The letter Y It works as a vowel when it’s at the end of a word so, it can form diphthongs as well. Hay, voy, ley, soy.

Common mistakes

For English natives, it’s very natural pronouncing diphthongs where they don’t exist in Spanish, mainly at the end of the words:

Spanish vowels pronunciation mistakes and how to fix them examples

  • The letter O is often pronounced as /əʊ/.
  • The letter E is pronounced as /ei/.

This is something that comes naturally to English native speakers, while we (Spaniards) tend to do the opposite when speaking in English. Remember, in Spanish 1 vowel = 1 sound. We never add extra sounds, in any case, we’d skip them!


If a diphthong is the combination of two vowels pronounced within the same syllable then, what is a triphthong?

That’s it! 3 vowels, side by side, pronounced in the same syllable.

Story (part 3): Alberto comes back home

Milu and his girlfriend are at home when suddenly Alberto comes back. The two mice run towards the corners of the room so that Alberto can fit in it.

The 3 of them form a triphthong.

The vowels which form triphthongs are always the same: closed + open + closed – or what is the same: (i/u) + (a/e/o) + (i/u). None of the two closed vowels has an accent mark (cheese), you’ll see why in the next post (hiatus).

Examples of Spanish triphthongs:
buey (buey)
criéis (criéis)
Paraguay (Pa.ra.guay)
limpiáis (lim.piáis)
actuáis (ac.tuáis)

Spanish triphthongs easy examples hiatus



  • 2 vowels pronounced in the same syllable.
  • Contains at least 1 closed vowel (i, u) without tilde.
    Examples: viernes, bueno, cuando, cianuro, hacéis.
  • May have no open vowel (a/e/o).
    Examples: viudo, cuidar, diurno, muy, fuimos, ciudad.


  • 3 vowels pronounced in the same syllable: (i/u) + (a/e/o) + (i/u).
  • Closed vowels (i, u) never carry a tilde.
    Examples: limpiéis, cambiáis, buey.

That’s it. Easy?

If you want to know when you should pronounce vowels in different syllables, you can read this post: Spanish hiatus.


Choose the group of words which contains only diphthongs:

Possible answers:

a) abuelo, zoo, miel
b) puedo, viento, bahía
c) cien, ahumado, tiempo
d) viaje, soleado, pie

(Click to see the answer)

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