Theta

Theta (UK: /ˈ θ iː t ə / , US: /ˈ θ eɪ t ə / ; uppercase Θ or ϴ, lowercase θ[note 1] 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 . In the system of Greek numerals, it has a value of 9.

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

In its archaic form, θ was written as a cross within a circle (as in the Etruscan or ), and later, as a line or point in circle ( or ). 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 , 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. Extensive lists of examples follow below at Mathematics and Science. U+03D1 ϑ GREEK THETA SYMBOL (script theta) is also common in biblical and theological usage e.g. πρόϑεσις instead of πρόθεσις (means placing in public or laying out a corpse).

In Latin script used for the Gaulish language, theta inspired the tau gallicum (). The phonetic value of the tau gallicum is thought to have been [t͡s] .[1] Theta itself is used alongside Latin letters in Halkomelem, a Native American language.

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

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.

The lowercase letter θ is used as a symbol for:

The uppercase letter Θ is used as a symbol for:

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 (, 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 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.

Greek Life

The names of many American fraternities and sororities are named with Greek letters, including Theta.

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.