The diaeresis is a diacritic sign, formed of two points, which is placed above a vowel. It indicates that two vowels, which follow one another, are pronounced separately one after the other.
Despite its apparent simplicity, it has long been mistreated in the French language. The umlaut comes from the ancient Greek, “trêmatos” which means “hole, hollow” It is first used to designate the points which appeared on the first dice.