Tau (/ˈtɔː, ˈtɒ, ˈtaʊ/;[1] uppercase Τ, lowercase τ or ; Greek: ταυ [taf]) is the nineteenth letter of the Greek alphabet, representing the voiceless dental or alveolar plosive IPA: [t]. In the system of Greek numerals, it has a value of 300.
The name in English is pronounced /taʊ/ or /tɔː/,[2] but in Greek it is [taf].[3][4] This is because the pronunciation of the combination of Greek letters αυ can have the pronunciation of either [ai], [av] or [af], depending on what follows and if a diaeresis is present on the second vowel (see Greek orthography).
Tau was derived from the Phoenician letter taw (𐤕).[5] Letters that arose from tau include Roman T and Cyrillic Te (Т, т).
The letter occupies the Unicode slots U+03C4 (lowercase) and U+03A4 (uppercase). In HTML, they can be produced with named entities (τ
and Τ
), decimal references (τ
and Τ
), or hexadecimal references (τ
and Τ
).
The lower-case letter τ is used as a symbol for:
For the Greek and Coptic letter tau:[17]
Preview | Τ | τ | Ⲧ | ⲧ | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | GREEK CAPITAL LETTER TAU | GREEK SMALL LETTER TAU | COPTIC CAPITAL LETTER TAU | COPTIC SMALL LETTER TAU | ||||
Encodings | decimal | hex | dec | hex | dec | hex | dec | hex |
Unicode | 932 | U+03A4 | 964 | U+03C4 | 11430 | U+2CA6 | 11431 | U+2CA7 |
UTF-8 | 206 164 | CE A4 | 207 132 | CF 84 | 226 178 166 | E2 B2 A6 | 226 178 167 | E2 B2 A7 |
Numeric character reference | Τ |
Τ |
τ |
τ |
Ⲧ |
Ⲧ |
ⲧ |
ⲧ |
Named character reference | Τ | τ | ||||||
DOS Greek | 147 | 93 | 171 | AB | ||||
DOS Greek-2 | 208 | D0 | 238 | EE | ||||
Windows 1253 | 212 | D4 | 244 | F4 | ||||
TeX | \tau |
For the mathematical letter tau:[18][19][20][21][22][23][24][25][26][27]
Preview | 𝚻 | 𝛕 | 𝛵 | 𝜏 | 𝜯 | 𝝉 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Unicode name | MATHEMATICAL BOLD CAPITAL TAU |
MATHEMATICAL BOLD SMALL TAU |
MATHEMATICAL ITALIC CAPITAL TAU |
MATHEMATICAL ITALIC SMALL TAU |
MATHEMATICAL BOLD ITALIC CAPITAL TAU |
MATHEMATICAL BOLD ITALIC SMALL TAU | ||||||
Encodings | decimal | hex | dec | hex | dec | hex | dec | hex | dec | hex | dec | hex |
Unicode | 120507 | U+1D6BB | 120533 | U+1D6D5 | 120565 | U+1D6F5 | 120591 | U+1D70F | 120623 | U+1D72F | 120649 | U+1D749 |
UTF-8 | 240 157 154 187 | F0 9D 9A BB | 240 157 155 149 | F0 9D 9B 95 | 240 157 155 181 | F0 9D 9B B5 | 240 157 156 143 | F0 9D 9C 8F | 240 157 156 175 | F0 9D 9C AF | 240 157 157 137 | F0 9D 9D 89 |
UTF-16 | 55349 57019 | D835 DEBB | 55349 57045 | D835 DED5 | 55349 57077 | D835 DEF5 | 55349 57103 | D835 DF0F | 55349 57135 | D835 DF2F | 55349 57161 | D835 DF49 |
Numeric character reference | 𝚻 |
𝚻 |
𝛕 |
𝛕 |
𝛵 |
𝛵 |
𝜏 |
𝜏 |
𝜯 |
𝜯 |
𝝉 |
𝝉 |
Preview | 𝝩 | 𝞃 | 𝞣 | 𝞽 | ||||
---|---|---|---|---|---|---|---|---|
Unicode name | MATHEMATICAL SANS-SERIF BOLD CAPITAL TAU |
MATHEMATICAL SANS-SERIF BOLD SMALL TAU |
MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL TAU |
MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL TAU | ||||
Encodings | decimal | hex | dec | hex | dec | hex | dec | hex |
Unicode | 120681 | U+1D769 | 120707 | U+1D783 | 120739 | U+1D7A3 | 120765 | U+1D7BD |
UTF-8 | 240 157 157 169 | F0 9D 9D A9 | 240 157 158 131 | F0 9D 9E 83 | 240 157 158 163 | F0 9D 9E A3 | 240 157 158 189 | F0 9D 9E BD |
UTF-16 | 55349 57193 | D835 DF69 | 55349 57219 | D835 DF83 | 55349 57251 | D835 DFA3 | 55349 57277 | D835 DFBD |
Numeric character reference | 𝝩 |
𝝩 |
𝞃 |
𝞃 |
𝞣 |
𝞣 |
𝞽 |
𝞽 |
These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.