Theta

n. eighth letter of the Greek alphabet

For other senses of this word, see theta (disambiguation).Theta (uppercase Θ, lowercase θ or ϑ) 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 , but in Koiné and later dialects it became a voiceless dental fricative . In American English, the name of the letter is commonly pronounced . In Modern Greek and British English, the name is pronounced .
See more at Wikipedia.org...

Noun
1. the 8th letter of the Greek alphabet
(hypernym) letter, letter of the alphabet, alphabetic character
(member-holonym) Greek alphabet

n. theta, eighth letter of the Greek alphabet

(n.)
A letter of the Greek alphabet corresponding to th in English; -- sometimes called the unlucky letter, from being used by the judges on their ballots in passing condemnation on a prisoner, it being the first letter of the Greek qa`natos, death.