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Webster 1913 Edition
Theta
The′ta
,Noun.
[L., fr. Gr.
θῆτα
, the Greek letter θ, Θ.] 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
θάνατος
, death. Theta function
(Math.)
, one of a group of functions used in developing the properties of elliptic functions.