In the traditional form, vowels are indicated by the weak consonants Aleph (), He (), Waw/Vav (), or Yodh () serving as vowel letters, or "matres lectionis": the letter is combined with a previous vowel and becomes silent, or by imitation of such cases in the spelling of other forms. Also, a system of vowel points to indicate vowels (diacritics), called niqqud, was developed. In modern forms of the alphabet, as in the case of Yiddish and to some extent Modern Hebrew, vowels may be indicated. Today, the trend is toward full spelling with the weak letters acting as true vowels.