Theta
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 For other senses of this word, see theta (disambiguation).
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, the name is pronounced /ˈθiːtə/. Letters such as the early Cyrillic letter fita (Ѳ, ѳ) developed from θ. In its archaic form, θ was written as:
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 ( 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]
SymbolThe lower-case letter θ is used as a symbol for:
The upper-case letter Θ is used as a symbol for:
In options investing
Theta is known as an option Greek measuring the rate of time decay on a daily basis. One can look at this as an ice cube melting in your hand. A Theta of −.05 means that the option is losing a nickel of time value each day. Other option Greeks include Delta, Vega, Rho and Gamma.[2]
In popular sociology
Theta is used colloquially to refer to the quotient of a person's appearance versus time.[citation needed] Similar to the Options investing as a description of the effect of time on price, Theta in this sense describes the effect of time on appearance. For example, a 50-year old woman, who looks as if she were 40 years old, would have a Theta of 50/40 = 1.20. An excellent example is Vanna White, who appears approximately 10 years younger than her calendar age. Theta is a desirable quality; people generally are more attracted to a person with good theta than those who look their age. Usage in names
References
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