Open and Closed Vowels – Concept, differences and syllables

We explain what open and closed vowels are, examples in words and how they form diphthongs, triphthongs and hiatuses.

open and closed vowels
The vowels are open or closed depending on how they are pronounced.

What are the open and closed vowels?

It is known as open and closed vowels, or also strong and weak vowels or low and high vowels, respectively, to the two types of vowels that distinguish international phonetics, depending on the ways in which the sound is made in the speech apparatus.

Remember that, unlike consonants, vowels are uninterrupted sound emissions, that is, not articulated, emerging together with the air column, with the oral cavity more or less open. The vowels in English are five: “a”, “e”, “i”, “o” and “u”, and they can be divided into open and closed, as follows:

  • Open, strong or low vowels. They are those that are made by placing the tongue in the lower part of the mouth, in its lowest possible position, thus expanding the oral cavity to produce the vowel sound. In English, the open vowels are “a”, “e” and “o”, although in some classifications the “e” can be considered as a middle or intermediate vowel.
  • Closed, weak or tall vowels. They are those that are made without the need for a great breadth of the oral cavity, so the tongue is placed in a higher position inside the mouth, without actually turning the sound into friction (as in fricative consonants). In English, the closed vowels are “i” and “u”.

Examples of words with open and closed vowels

Here is a short list of word examples with each of the open and closed vowels:

Words with open vowels:

  • Words with “a”: able, ache, acre, acorn, also, apricot.
  • Words with “e”: emit, emission, equator, enunciate, equinox.
  • Words with “o”: obey, ocean, odor, Ohio, October.

Words with closed vowels:

  • Words with “b”: backing, basil, basket, bassoon, bistro, Boston, boxer
  • Words with “l”: lapdog, laptop, lemon, lesson, letter, level, lintel, liver, lobby, locker


A diphthong is called an acoustic phenomenon that consists of a sound chain formed by two contiguous vowels, which constitute the same syllable and therefore cannot be pronounced separately. For diphthongs to occur, the two vowels must be next to each other and must be, in English, necessarily one of the following cases:

  • “aw”/”au”: straw, law, saw, cause, haul, author
  • “oy”/”oi”: toy, boy, coy, coin, noise, oil
  • “ow”/”ou”: cow, now, flower, cloud, house, loud


Similar to diphthong, triphthong is an acoustic phenomenon in which three vowels make up the same syllable and are therefore pronounced consecutively and inseparably. These cases are rarer than those of the diphthong, and in English they are necessarily formed by the union of a weak vowel, a strong and a weak vowel, in that precise strict order.

Examples of words with tripthong are:

  • “hour” – compared with disyllabic “shower”
  • “fire”  – compared with disyllabic “higher”
  • “loir” – compared with final disyllabic sequence in “employer”


If the diphthong is the union in the same syllable of two contiguous vowels, the hiatus is the opposite: the separation of two contiguous vowels into different syllables, by effect of its sound forces. For this to happen, in English, there must be a loanword from another language, like so:

  • coöperate, daïs and reëlect, examples usually replaced by a hypen.
  • naïve or naïvety, a special case scenario.
  • proper nouns, like Noël, Zoë or Chloë.