diaeresis

/daɪˈɛrəsɪs/
noun
  1. A mark (¨) placed over a vowel to show that it is pronounced separately from the preceding vowel, as in 'naïve' or 'coöperate'.
    • Some writers use a diaeresis in 'coöperate' to indicate two distinct vowel sounds.
    • In older English, a diaeresis was more common in words like 'reëlect'.
    • The word 'naïve' has a diaeresis over the 'i' to show it is pronounced separately.
  2. The pronunciation of two adjacent vowels as separate syllables rather than as a single sound.
    • The diaeresis in 'aërial' makes it a three-syllable word.
    • Linguists study diaeresis as a feature of poetic meter.
    • Without a diaeresis, 'noël' might be mispronounced as a single syllable.
What does "diaeresis" mean? | whatsthatwordmean | whatsthatwordmean