The voiceless alveolar stop is a type of consonantal sound used in many spoken languages. The symbol in the International Phonetic Alphabet that represents voiceless dental, alveolar, and postalveolar stops is , and the equivalent X-SAMPA symbol is t. The dental stop can be distinguished with the underbridge diacritic, , the postalveolar with a retraction line, , and the Extensions to the IPA have a double underline diacritic which can be used to explicitly specify an alveolar pronunciation, .