The Voiceless dental fricative reference article from the English Wikipedia on 24-Apr-2004
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Voiceless dental fricative

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The voiceless dental fricative is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is θ, and the equivalent X-SAMPA symbol is T. The voiceless dental fricative occurs in English, and it is the sound denoted by the letters "th" in thing and bath. It is different from the "th" sound in this and the, which is the voiced dental fricative. The dental fricatives are often called "interdental" because they are often produced with the tongue between the upper and lower teeth, and not just against the back of the teeth, as they are with other dental consonants.

IPA - Unicode θ
IPA - image Image:Xsampa-T2.png
X-SAMPA T
Sound sample

Features of this consonant: