Pi (letter)

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Pi (/ˈp/; Greek: [pi], uppercase Π, lowercase π) is the sixteenth letter of the Greek alphabet, representing [p]. In the system of Greek numerals it has a value of 80. It was derived from the Phoenician letter pe Phoenician pe.svg. Letters that arose from pi include Cyrillisexc Pe (П, п), Coptic pi (Ⲡ, ⲡ), and Gothic pairthra (𐍀).

Symbol

The upper-case letter Π is used as a symbol for:

The lower-case letter π is used as a symbol for:

History

An early form of pi was Greek Pi archaic.svg, appearing almost like a gamma with a hook.

In the book 'L'alphabet grec', T. H. de Mortain speculates that letter П is a gate, since it is the first letter of "πύλη" (gate of town or temple). Allegedly, the Greeks wanted to represent the shape of the entrance to civilization, such as the gate of the lions in Mycenae. This hypothesis is not shared by any other authority in the field and has no other attestation.

Variant pi

Variant pi or "pomega" (\varpi\,\! or ϖ) is a glyph variant of lower case pi sometimes used in technical contexts as though it were a lower-case omega with a macron, though historically it is simply a cursive form of pi, with its legs bent inward to meet. It is used as a symbol for:

The various forms of pi are present in Unicode as:

  • U+03A0 Π GREEK CAPITAL LETTER PI (HTML &#928;<dot-separator> &Pi;)
  • U+03C0 π GREEK SMALL LETTER PI (HTML &#960;<dot-separator> &pi;)
  • U+03D6 ϖ GREEK PI SYMBOL (HTML &#982;<dot-separator> &piv;)
  • U+220F N-ARY PRODUCT (HTML &#8719;<dot-separator> &prod;)
  • U+1D28 GREEK LETTER SMALL CAPITAL PI (HTML &#7464;)
  • U+1D70B 𝜋 MATHEMATICAL ITALIC SMALL PI (HTML &#120587;)
  • U+1D6D1 𝛑 MATHEMATICAL BOLD SMALL PI (HTML &#120529;).[3]

Character Encodings

  • Greek / Coptic Pi[4]
Character Π π ϖ
Unicode name GREEK CAPITAL LETTER PI GREEK SMALL LETTER PI GREEK PI SYMBOL COPTIC CAPITAL LETTER PI COPTIC SMALL LETTER PI
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 928 U+03A0 960 U+03C0 982 U+03D6 11424 U+2CA0 11425 U+2CA1
UTF-8 206 160 CE A0 207 128 CF 80 207 150 CF 96 226 178 160 E2 B2 A0 226 178 161 E2 B2 A1
Numeric character reference &#928; &#x3A0; &#960; &#x3C0; &#982; &#x3D6; &#11424; &#x2CA0; &#11425; &#x2CA1;
Named character reference &Pi; &pi; &piv;
DOS Greek 143 8F 167 A7
DOS Greek-2 198 C6 234 EA
Windows 1253 208 D0 240 F0
TeX \Pi \pi \varpi
  • Mathematical Pi
Character 𝚷 𝛑 𝛱 𝜋
Unicode name N-ARY PRODUCT N-ARY COPRODUCT MATHEMATICAL BOLD
CAPITAL PI
MATHEMATICAL BOLD
SMALL PI
MATHEMATICAL ITALIC
CAPITAL PI
MATHEMATICAL ITALIC
SMALL PI
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 8719 U+220F 8720 U+2210 120503 U+1D6B7 120529 U+1D6D1 120561 U+1D6F1 120587 U+1D70B
UTF-8 226 136 143 E2 88 8F 226 136 144 E2 88 90 240 157 154 183 F0 9D 9A B7 240 157 155 145 F0 9D 9B 91 240 157 155 177 F0 9D 9B B1 240 157 156 139 F0 9D 9C 8B
UTF-16 8719 220F 8720 2210 55349 57015 D835 DEB7 55349 57041 D835 DED1 55349 57073 D835 DEF1 55349 57099 D835 DF0B
Numeric character reference &#8719; &#x220F; &#8720; &#x2210; &#120503; &#x1D6B7; &#120529; &#x1D6D1; &#120561; &#x1D6F1; &#120587; &#x1D70B;
Named character reference &prod;
Character 𝜫 𝝅 𝝥 𝝿 𝞟 𝞹
Unicode name MATHEMATICAL BOLD ITALIC
CAPITAL PI
MATHEMATICAL BOLD ITALIC
SMALL PI
MATHEMATICAL SANS-SERIF
BOLD CAPITAL PI
MATHEMATICAL SANS-SERIF
BOLD SMALL PI
MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL PI
MATHEMATICAL SANS-SERIF
BOLD ITALIC SMALL PI
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 120619 U+1D72B 120645 U+1D745 120677 U+1D765 120703 U+1D77F 120735 U+1D79F 120761 U+1D7B9
UTF-8 240 157 156 171 F0 9D 9C AB 240 157 157 133 F0 9D 9D 85 240 157 157 165 F0 9D 9D A5 240 157 157 191 F0 9D 9D BF 240 157 158 159 F0 9D 9E 9F 240 157 158 185 F0 9D 9E B9
UTF-16 55349 57131 D835 DF2B 55349 57157 D835 DF45 55349 57189 D835 DF65 55349 57215 D835 DF7F 55349 57247 D835 DF9F 55349 57273 D835 DFB9
Numeric character reference &#120619; &#x1D72B; &#120645; &#x1D745; &#120677; &#x1D765; &#120703; &#x1D77F; &#120735; &#x1D79F; &#120761; &#x1D7B9;

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.

See also

References

  1. Lua error in package.lua at line 80: module 'strict' not found.
  2. Outline for Weeks 14&15, Astronomy 225 Spring 2008
  3. Lua error in package.lua at line 80: module 'strict' not found.
  4. Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)