Theta

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Theta uc lc.svg
Greek alphabet
Αα Alpha Νν Nu
Ββ Beta Ξξ Xi
Γγ Gamma Οο Omicron
Δδ Delta Ππ Pi
Εε Epsilon Ρρ Rho
Ζζ Zeta Σσς Sigma
Ηη Eta Ττ Tau
Θθ Theta Υυ Upsilon
Ιι Iota Φφ Phi
Κκ Kappa Χχ Chi
Λλ Lambda Ψψ Psi
Μμ Mu Ωω Omega
History
Archaic local variants
  • Digamma
  • Heta
  • San
  • Koppa
  • Sampi
  • Tsan
Numerals
ϛ (6)
ϟ (90)
ϡ (900)
In other languages
Scientific symbols

Theta (uppercase Θ, lowercase θ or ϑ;1 Ancient Greek θῆτα [tʰɛ̂ːta]; Modern Greek θήτα [ˈθita]; UK /ˈθtə/, US /ˈθtə/) is the eighth letter of the Greek alphabet, derived from the Phoenician letter Teth Phoenician teth.svg. In the system of Greek numerals it has a value of 9.

Greek

The alphabet on a black figure vessel, with a point-and-circle theta.

In Ancient Greek, θ represented the aspirated voiceless dental plosive /t̪ʰ/, but in Modern Greek it represents the voiceless dental fricative /θ/.

Forms

In its archaic form, θ was written as a cross within a circle (A symbol of a cross within a circle or Another symbol of a cross within a circle), and later, as a line or point within a circle (The symbol of a line within a circle or The symbol of a point within a circle).

Latin

The name ARAÐÐOVNA on a Gaulish tombstone.

In the Latin script used for the Gaulish language, theta developed into the tau gallicum, conventionally transliterated as Ð, although the bar extends across the centre of the letter. The phonetic value of the tau gallicum is thought to have been [t͡s].

Cyrillic

The early Cyrillic letter fita (Ѳ, ѳ) developed from θ.

International Phonetic Alphabet

In the International Phonetic Alphabet, [θ] represents the voiceless dental fricative, as in thick or thin. It does not represent the consonant in the, which is the voiced dental fricative.

Math and science

Lower case

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

Upper case

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

In its archaic form

  • In its archaic form (A symbol of a cross within a circle) theta is used as a symbol for Earth.

Greek mathematics

The common usage of theta in mathematical problems began with the Greeks. They logically chose this Greek symbol since it was the next in their alphabet not yet used and was easily legible when recreating for multiple uses.

Archaic crossed forms of theta are seen in the wheel letters of Linear A, Linear B, and Egyptian hieroglyphics, the mathematical tensor product, exclusive disjunction, and direct sum operators, the identification symbol for the Earth (as already mentioned), and the Celtic cross. The circumpunct, or circled dot, is seen in a wide range of places.

Symbolism

θ (θάνατος, death) in an mosaic
  • In ancient times, Tau was used as a symbol for life and/or resurrection, whereas the eighth letter of the Greek alphabet, theta, was considered the symbol of death.

According to Porphyry of Tyros, the Egyptians used an X within a circle as a symbol of the soul; having a value of nine, it was used as a symbol for Ennead. Johannes Lydus says that the Egyptians used a symbol for Kosmos in the form of theta, with a fiery circle representing the world, and a snake spanning the middle representing Agathos Daimon (literally: good spirit).2

The Egyptians also used the symbol of a point within a circle (The symbol of a point within a circle, the sun disc) to represent the sun, which might be a possible origin of its use as the Sun's astrological glyph. It is worthwhile to note that θῆτα (theta) has the same numerical value in isopsephy as Ηλιος (Helios): 318.

In modern times, L. Ron Hubbard's teachings of Scientology have expanded on the concept of a soul, or thetan (derived from the Greek letter "theta").

Abbreviation

In classical Athens, it was used as an abbreviation for the Greek θάνατος (thanatos, “death”) and as it vaguely resembles a human skull,citation needed theta was used as a warning symbol of death, in the same way that skull and crossbones are used in modern times. It survives on potsherds used by Athenians when voting for the death penalty.2 Petrus de Dacia in a document from 1291 relates the idea that theta was used to brand criminals as empty ciphers, and the branding rod was affixed to the crossbar spanning the circle.3 For this reason, use of the number theta was sometimes avoided where the connotation was felt to be unlucky - the mint marks of some Late Imperial Roman coins famously have the sum ΔΕ or ΕΔ (delta and epsilon, that is 4 and 5) substituted as a euphemism where a Θ (9) would otherwise be expected.

Character Encodings

  • Greek Theta
Character Θ θ ϑ ϴ ᶿ
Unicode name GREEK CAPITAL LETTER THETA GREEK SMALL LETTER THETA GREEK THETA SYMBOL GREEK CAPITAL THETA SYMBOL MODIFIER LETTER SMALL THETA
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 920 U+0398 952 U+03B8 977 U+03D1 1012 U+03F4 7615 U+1DBF
UTF-8 206 152 CE 98 206 184 CE B8 207 145 CF 91 207 180 CF B4 225 182 191 E1 B6 BF
Numeric character reference Θ Θ θ θ ϑ ϑ ϴ ϴ ᶿ ᶿ
Named character reference Θ θ ϑ
DOS Greek 135 87 159 9F
DOS Greek-2 172 AC 226 E2
Windows 1253 200 C8 232 E8
TeX \Theta \theta \vartheta
  • Coptic Thethe
Character
Unicode name COPTIC CAPITAL LETTER THETHE COPTIC SMALL LETTER THETHE
Encodings decimal hex decimal hex
Unicode 11408 U+2C90 11409 U+2C91
UTF-8 226 178 144 E2 B2 90 226 178 145 E2 B2 91
Numeric character reference Ⲑ Ⲑ ⲑ ⲑ
  • Cyrillic Fita
Character Ѳ ѳ
Unicode name CYRILLIC CAPITAL LETTER FITA CYRILLIC SMALL LETTER FITA
Encodings decimal hex decimal hex
Unicode 1138 U+0472 1139 U+0473
UTF-8 209 178 D1 B2 209 179 D1 B3
Numeric character reference Ѳ Ѳ ѳ ѳ
  • Mathematical Theta
Character 𝚯 𝛉 𝚹 𝛝
Unicode name MATHEMATICAL BOLD
CAPITAL THETA
MATHEMATICAL BOLD
SMALL THETA
MATHEMATICAL BOLD
CAPITAL THETA SYMBOL
MATHEMATICAL BOLD
THETA SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120495 U+1D6AF 120521 U+1D6C9 120505 U+1D6B9 120541 U+1D6DD
UTF-8 240 157 154 175 F0 9D 9A AF 240 157 155 137 F0 9D 9B 89 240 157 154 185 F0 9D 9A B9 240 157 155 157 F0 9D 9B 9D
UTF-16 55349 57007 D835 DEAF 55349 57033 D835 DEC9 55349 57017 D835 DEB9 55349 57053 D835 DEDD
Numeric character reference 𝚯 𝚯 𝛉 𝛉 𝚹 𝚹 𝛝 𝛝
Character 𝛩 𝜃 𝛳 𝜗
Unicode name MATHEMATICAL ITALIC
CAPITAL THETA
MATHEMATICAL ITALIC
SMALL THETA
MATHEMATICAL ITALIC
CAPITAL THETA SYMBOL
MATHEMATICAL ITALIC
THETA SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120553 U+1D6E9 120579 U+1D703 120563 U+1D6F3 120599 U+1D717
UTF-8 240 157 155 169 F0 9D 9B A9 240 157 156 131 F0 9D 9C 83 240 157 155 179 F0 9D 9B B3 240 157 156 151 F0 9D 9C 97
UTF-16 55349 57065 D835 DEE9 55349 57091 D835 DF03 55349 57075 D835 DEF3 55349 57111 D835 DF17
Numeric character reference 𝛩 𝛩 𝜃 𝜃 𝛳 𝛳 𝜗 𝜗
Character 𝜣 𝜽 𝜭 𝝑
Unicode name MATHEMATICAL BOLD ITALIC
CAPITAL THETA
MATHEMATICAL BOLD ITALIC
SMALL THETA
MATHEMATICAL BOLD ITALIC
CAPITAL THETA SYMBOL
MATHEMATICAL BOLD ITALIC
CAPITAL THETA SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120611 U+1D723 120637 U+1D73D 120621 U+1D72D 120657 U+1D751
UTF-8 240 157 156 163 F0 9D 9C A3 240 157 156 189 F0 9D 9C BD 240 157 156 173 F0 9D 9C AD 240 157 157 145 F0 9D 9D 91
UTF-16 55349 57123 D835 DF23 55349 57149 D835 DF3D 55349 57133 D835 DF2D 55349 57169 D835 DF51
Numeric character reference 𝜣 𝜣 𝜽 𝜽 𝜭 𝜭 𝝑 𝝑
Character 𝝝 𝝷 𝝧 𝞋
Unicode name MATHEMATICAL SANS-SERIF
BOLD CAPITAL THETA
MATHEMATICAL SANS-SERIF
BOLD SMALL THETA
MATHEMATICAL SANS-SERIF
BOLD CAPITAL THETA SYMBOL
MATHEMATICAL SANS-SERIF
BOLD THETA SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120669 U+1D75D 120695 U+1D777 120679 U+1D767 120715 U+1D78B
UTF-8 240 157 157 157 F0 9D 9D 9D 240 157 157 183 F0 9D 9D B7 240 157 157 167 F0 9D 9D A7 240 157 158 139 F0 9D 9E 8B
UTF-16 55349 57181 D835 DF5D 55349 57207 D835 DF77 55349 57191 D835 DF67 55349 57227 D835 DF8B
Numeric character reference 𝝝 𝝝 𝝷 𝝷 𝝧 𝝧 𝞋 𝞋
Character 𝞗 𝞱 𝞡 𝟅
Unicode name MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL THETA
MATHEMATICAL SANS-SERIF
BOLD ITALIC SMALL THETA
MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL THETA SYMBOL
MATHEMATICAL SANS-SERIF
BOLD ITALIC THETA SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex
Unicode 120727 U+1D797 120753 U+1D7B1 120737 U+1D7A1 120773 U+1D7C5
UTF-8 240 157 158 151 F0 9D 9E 97 240 157 158 177 F0 9D 9E B1 240 157 158 161 F0 9D 9E A1 240 157 159 133 F0 9D 9F 85
UTF-16 55349 57239 D835 DF97 55349 57265 D835 DFB1 55349 57249 D835 DFA1 55349 57285 D835 DFC5
Numeric character reference 𝞗 𝞗 𝞱 𝞱 𝞡 𝞡 𝟅 𝟅

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

Notes

  1. ^ Unicode keeps U+03D1 ϑ "GREEK THETA SYMBOL" ("=script theta") separate from U+03B8 θ "GREEK SMALL LETTER THETA". For the purpose of writing Greek text, the two can be considered font variants, but θ and ϑ can be distinct as symbols in technical or mathematical use.
  2. ^ a b Barry, Kieren (1999), The Greek Qabalah: Alphabetic Mysticism and Numerology in the Ancient World, Samuel Weiser, p. 73, ISBN 1-57863-110-6 .
  3. ^ Kaplan, Robert (2000), The Nothing that Is: A Natural History of Zero, Oxford; New York: Oxford University Press, p. 66, Bibcode:2000tnti.book.....K, ISBN 0-19-514237-3 .







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