The Full Wiki

Theta: Wikis


Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.


From Wikipedia, the free encyclopedia

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
Obsolete letters
Digamma uc lc.svg Digamma Qoppa uc lc.svg Qoppa
San uc lc.svg San Sampi uc lc.svg Sampi
Other characters
Stigma uc lc.svg Stigma Sho uc lc.svg Sho
Heta uc lc.svg Heta

Greek diacritics

Theta (uppercase Θ, lowercase θ or ϑ; Greek: Θήτα) 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 Classical Greek θ represented an aspirated voiceless dental plosive (/t̪ʰ/), but in Koiné and later dialects it became a voiceless dental fricative /θ/. In American English the name of the letter is commonly pronounced /ˈθeɪtə/. In British English, it is pronounced /ˈθiːtə/.

Letters such as the early Cyrillic letter fita (Ѳ, ѳ) developed from θ.

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).

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).[1]

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 classical Athens, it was used as an abbreviation for the Greek θάνατος (thanatos, “death”) and as it vaguely resembles a human skull, 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.[1] 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.[2]


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

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

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 astrological symbol for the Earth (as already mentioned), and the Celtic cross. The circumpunct, or circled dot, is seen in a wide range of places.


  1. ^ 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 .
  2. ^ Kaplan, Robert (2000), The Nothing that Is: A Natural History of Zero, Oxford University Press, pp. 66, ISBN 0-1951-4237-3 .

See also



Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also theta


German Wikipedia has an article on:

Wikipedia de


Theta n.

  1. theta (greek letter)

Simple English

Theta is the eighth Greek letter, written Θ (uppercase) or θ (lowercase).

Theta also refers to:

  • Theta, South Africa
  • Theta wave
  • GM Theta platform
  • Potential temperature
  • Kappa Alpha Theta
  • Theta role
  • Theta (band)
  • Theta probe for measuring soil moisture


Got something to say? Make a comment.
Your name
Your email address