Difference Between Diphthong and Adipthong

Words are essential structures for language and obviously, when used in an orderly and coherent way, they form phrases and sentences. Words are made up of a -root-, which is the part that does not vary and gives a lexical meaning to the word, and also by morphemes, which are the variable part and give it a grammatical meaning to form new words.

In this sense, words are used to define some object, idea or action and can be divided into syllables, the latter being a group of sounds that are pronounced in a single stroke of voice. Additionally, within the syllables, diphthongs and adiphthongs or hiatus can be identified, which have characteristics that differentiate one from the other, depending on the union of open or closed vowels.

Therefore, in this article we are going to show the differences between diphthongs and adiphthongs based on their definitions.


It is the union of two closed vowels (such as iu), one open and one closed (such as ai) or one closed and one open (such as ua) in the same syllable. Likewise, there are several types of diphthongs, such as:

  • The accented growing diphthong : when the closed vowel is tone and precedes the open one (have mercy).
  • The unaccented growing diphthong : when the closed vowel precedes the open one without any of them having accentuation (study).
  • Stressed decreasing diphthongs : they have the stressed open vowel and the unstressed closed vowel (caiga).
  • Unaccented decreasing diphthongs : when the open vowel precedes the closed one without any stress (landscape).
  • Homogeneous diphthongs : they are formed with two closed vowels in which none is stressed (widower).


Also known as -hiatus- and occurs when two vowels are found together in the same word but in different syllables. However, for the hiatus to occur within a word, some of these conditions must be met:

  • By the union of a stressed closed vowel and an unstressed open vowel (like river)
  • By the union of two different open vowels (as drama)
  • By the union of an unstressed open vowel and a stressed closed vowel (as a root)
  • By the union of two equal open or closed vowels (like read me, Shia).

It should be noted that the letter “h” between two vowels does not break the diphthong or the hiatus. In conclusion, some important differences between the Diphthong and the Adipthong or Hiatus are shown:

Diphthong adiphthong
In the diphthong, the vowels together must remain in the same syllable. In the adiphthong, the vowels together must remain in different syllables.
The diphthong is formed when an open vowel and a closed vowel come together. The adiphthong is formed with the combination of an open vowel and a closed vowel with a tilde.
The diphthong is formed when two different closed vowels are combined without accents. The adiphthong is formed when two equal open or closed vowels are combined and one of them with a tilde.

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