from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The eighth letter of the Greek alphabet. See Table at alphabet.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. the name for the eighth letter οf the Modern Greek alphabet, ninth in Old Greek.
  • n. The measure of an angle.

from the GNU version of the Collaborative International Dictionary of English

  • 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.

from The Century Dictionary and Cyclopedia

  • n. As used in formulæ of mathematics and engineering, theta (θ) usually denotes:
  • n. the entropy, or thermodynamic function or factor by which the absolute temperature is to be multiplied to indicate an amount of heat energy.
  • n. The angle, in angular measure, or at the center, through which a radius vector has swept from a zero position, or through which a line has swept in a rotation.
  • n. A letter of the Greek alphabet corresponding to the English th in thin, etc.
  • n. A sort of complication of an exponential function, being expressed by a series from n =—∞ to n = + ∞ of terms the logarithm of each of which is na + 2 na. A theta function of several variables, x1, x2, … xn, is Σ exp. (φ + Σmxn xn), where φ is a quadratic function of the constants m1, m2, … mn.
  • n. A function which occurs in probabilities, and is expressed by the integral fe—tdt.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the 8th letter of the Greek alphabet


from The American Heritage® Dictionary of the English Language, 4th Edition

Greek thēta, of Phoenician origin; akin to Hebrew ṭêt, teth.

from Wiktionary, Creative Commons Attribution/Share-Alike License

From the Ancient Greek θῆτα (thēta).


  • If you are reading something, language areas oscillate in theta frequency allowing high-gamma-related neural activity in individual neurons to transmit information, said Knight.

    Slow Brain Waves are Key to Complex Activities | Impact Lab

  • This temperature Professor Flory named the theta temperature.

    The Nobel Prize in Chemistry 1974 - Presentation Speech

  • The stimulation also increased so-called theta waves in the hippocampus, a low-frequency global rhythm that seems to coordinate the firing of neurons and aid memory.

    NYT > Home Page

  • As the number of drones and the pace of instructions increases, the brain shows sharp spikes in a kind of electrical activity called theta - cause for concern among the researchers.

    NYT > Home Page

  • We also see that the theta is a nice +.0041 so this trade will pay us a nice +.0041 to hold.

    Trading Rules in the Quest for Profits - Yahoo! Finance

  • Time value, also known as theta, melts a little each day. Headlines

  • The researchers discovered that when a sound was restored perceptually (ie when the participant "heard" it), slow brain waves called theta oscillations, which occur when the brain is encoding boundaries of sound, were suppressed during the interruption of that sound.

    Health News from Medical News Today

  • They found that slow brain waves called theta oscillations, which are involved in encoding boundaries of sounds, were suppressed during an interruption in a sound when that sound was illusorily restored.

    Daily News & Analysis

  • Researchers at J-PARC will be attempting to measure the oscillation from muon neutrino to electron neutrino - the final "mixing angle" yet to be measured, known as theta-13. all content

  • The researchers found that, by imposing a normal "theta" rhythm on epileptic rats, they reduced seizures by 86-97 percent.

    Science press releases


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