Theta

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Theta ( UK: /ˈθtə/ , US: /ˈθtə/ ; uppercase Θ or ϴ, lowercase θ (which resembles digit 0 with horizontal line) or ϑ; Ancient Greek : θῆτα thē̂ta [tʰɛ̂ːta] ; Modern: θήτα thī́ta [ˈθita] ) 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 the value 9.

Contents

Greek

The alphabet on a black figure vessel, with a point-and-circle theta. NAMA Alphabet grec.jpg
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 (as in the Etruscan Earth symbol.svg or Cross within circle 2.svg ), and later, as a line or point in circle ( Line within circle.svg or Sun symbol.svg ). Archaic crossed forms of theta are seen in the wheel letters of Linear A and Linear B.

The cursive form ϑ was retained by Unicode as 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 font variants of a single character, but θ and ϑ are also used as distinct symbols in technical and mathematical contexts.

Latin

The name ARADDOVNA on a Gaulish tombstone. Tau gallic CourDOr Metz 3147.jpg
The name ARAÐÐOVNA on a Gaulish tombstone.

In Latin script used for the Gaulish language, theta developed into the tau gallicum, conventionally transliterated as Ð (eth), although the bar extends across the centre of the letter. The phonetic value of the tau gallicum is thought to have been [t͡s]. In March, 2020 Unicode added four characters to represent tau gallicum: [1]

Cyrillic

The early Cyrillic letter fita (Ѳ, ѳ) developed from θ. This letter existed in the Russian alphabet until the 1918 Russian orthography reform.

International Phonetic Alphabet

In the International Phonetic Alphabet (IPA), [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. A similar-looking symbol, [ɵ], which is described as a lowercase barred o, indicates in the IPA a close-mid central rounded vowel.

Mathematics and science

Lower case

The lowercase letter θ is used as a symbol for:

Upper case

The uppercase letter Θ is used as a symbol for:

Symbolism

th (thanatos, death) in a mosaic Retiarius vs secutor from Borghese mosaic.jpg
θ (θάνατος, death) in a mosaic

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). [3]

The Egyptians also used the symbol of a point within a circle ( Sun symbol.svg , 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.

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. [3] 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. [4] 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

Character information
PreviewΘθϑϴᶿ
Unicode nameGREEK CAPITAL LETTER THETAGREEK SMALL LETTER THETAGREEK THETA SYMBOLGREEK CAPITAL THETA SYMBOLMODIFIER LETTER SMALL THETA
Encodingsdecimalhexdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 920U+0398952U+03B8977U+03D11012U+03F47615U+1DBF
UTF-8 206 152CE 98206 184CE B8207 145CF 91207 180CF B4225 182 191E1 B6 BF
Numeric character reference ΘΘθθϑϑϴϴᶿᶿ
Named character reference Θθϑ, ϑ, ϑ
DOS Greek135871599F
DOS Greek-2172AC226E2
Windows 1253200C8232E8
TeX\Theta\theta\vartheta
  • Coptic Thethe
Character information
Preview
Unicode nameCOPTIC CAPITAL LETTER THETHECOPTIC SMALL LETTER THETHE
Encodingsdecimalhexdecimalhex
Unicode 11408U+2C9011409U+2C91
UTF-8 226 178 144E2 B2 90226 178 145E2 B2 91
Numeric character reference ⲐⲐⲑⲑ
  • Cyrillic Fita
Character information
PreviewѲѳ
Unicode nameCYRILLIC CAPITAL LETTER FITACYRILLIC SMALL LETTER FITA
Encodingsdecimalhexdecimalhex
Unicode 1138U+04721139U+0473
UTF-8 209 178D1 B2209 179D1 B3
Numeric character reference ѲѲѳѳ
  • Mathematical Theta
Character information
Preview𝚯𝛉𝚹𝛝
Unicode nameMATHEMATICAL BOLD
CAPITAL THETA
MATHEMATICAL BOLD
SMALL THETA
MATHEMATICAL BOLD
CAPITAL THETA SYMBOL
MATHEMATICAL BOLD
THETA SYMBOL
Encodingsdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 120495U+1D6AF120521U+1D6C9120505U+1D6B9120541U+1D6DD
UTF-8 240 157 154 175F0 9D 9A AF240 157 155 137F0 9D 9B 89240 157 154 185F0 9D 9A B9240 157 155 157F0 9D 9B 9D
UTF-16 55349 57007D835 DEAF55349 57033D835 DEC955349 57017D835 DEB955349 57053D835 DEDD
Numeric character reference 𝚯𝚯𝛉𝛉𝚹𝚹𝛝𝛝
Character information
Preview𝛩𝜃𝛳𝜗
Unicode nameMATHEMATICAL ITALIC
CAPITAL THETA
MATHEMATICAL ITALIC
SMALL THETA
MATHEMATICAL ITALIC
CAPITAL THETA SYMBOL
MATHEMATICAL ITALIC
THETA SYMBOL
Encodingsdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 120553U+1D6E9120579U+1D703120563U+1D6F3120599U+1D717
UTF-8 240 157 155 169F0 9D 9B A9240 157 156 131F0 9D 9C 83240 157 155 179F0 9D 9B B3240 157 156 151F0 9D 9C 97
UTF-16 55349 57065D835 DEE955349 57091D835 DF0355349 57075D835 DEF355349 57111D835 DF17
Numeric character reference 𝛩𝛩𝜃𝜃𝛳𝛳𝜗𝜗
Character information
Preview𝜣𝜽𝜭𝝑
Unicode nameMATHEMATICAL BOLD ITALIC
CAPITAL THETA
MATHEMATICAL BOLD ITALIC
SMALL THETA
MATHEMATICAL BOLD ITALIC
CAPITAL THETA SYMBOL
MATHEMATICAL BOLD ITALIC
CAPITAL THETA SYMBOL
Encodingsdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 120611U+1D723120637U+1D73D120621U+1D72D120657U+1D751
UTF-8 240 157 156 163F0 9D 9C A3240 157 156 189F0 9D 9C BD240 157 156 173F0 9D 9C AD240 157 157 145F0 9D 9D 91
UTF-16 55349 57123D835 DF2355349 57149D835 DF3D55349 57133D835 DF2D55349 57169D835 DF51
Numeric character reference 𝜣𝜣𝜽𝜽𝜭𝜭𝝑𝝑
Character information
Preview𝝝𝝷𝚹𝞋
Unicode nameMATHEMATICAL SANS-SERIF
BOLD CAPITAL THETA
MATHEMATICAL SANS-SERIF
BOLD SMALL THETA
MATHEMATICAL SANS-SERIF
BOLD CAPITAL THETA SYMBOL
MATHEMATICAL SANS-SERIF
BOLD THETA SYMBOL
Encodingsdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 120669U+1D75D120695U+1D777120505U+1D6B9120715U+1D78B
UTF-8 240 157 157 157F0 9D 9D 9D240 157 157 183F0 9D 9D B7240 157 154 185F0 9D 9A B9240 157 158 139F0 9D 9E 8B
UTF-16 55349 57181D835 DF5D55349 57207D835 DF7755349 57017D835 DEB955349 57227D835 DF8B
Numeric character reference 𝝝𝝝𝝷𝝷𝚹𝚹𝞋𝞋
Character information
Preview𝞗𝞱𝜭𝟅
Unicode nameMATHEMATICAL 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
Encodingsdecimalhexdecimalhexdecimalhexdecimalhex
Unicode 120727U+1D797120753U+1D7B1120621U+1D72D120773U+1D7C5
UTF-8 240 157 158 151F0 9D 9E 97240 157 158 177F0 9D 9E B1240 157 156 173F0 9D 9C AD240 157 159 133F0 9D 9F 85
UTF-16 55349 57239D835 DF9755349 57265D835 DFB155349 57133D835 DF2D55349 57285D835 DFC5
Numeric character reference 𝞗𝞗𝞱𝞱𝜭𝜭𝟅𝟅

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. Everson, Michael; Lilley, Chris (2019-05-26). "L2/19-179: Proposal for the addition of four Latin characters for Gaulish" (PDF).
  2. http://math.stanford.edu/~feferman/papers/id-saga.pdf
  3. 1 2 Barry, Kieren (1999), The Greek Qabalah: Alphabetic Mysticism and Numerology in the Ancient World, Samuel Weiser, p. 73, ISBN   1-57863-110-6 .
  4. 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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Fita archaic Cyrillic letter

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The (Cyrillic) Cyrillic letter

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The null sign U+2205EMPTY SET denotes the empty set in mathematics. The same letter in linguistics represents zero, the lack of an element. It is commonly used in phonology, morphology, and syntax.