The IPA is designed to represent only those qualities of speech that are distinctive in spoken language: phonemes, intonation, and the separation of words and syllables. To represent additional qualities of speech such as tooth gnashing, lisping, and sounds made with a cleft palate, an extended set of symbols called the Extensions to the IPA is used. Occasionally symbols are added, removed, or modified by the International Phonetic Association. As of 2008, there are 107 distinct letters, 52 diacritics, and four prosody marks in the IPA proper.