Definition of theta in English:



  • 1The eighth letter of the Greek alphabet (Θ, θ), transliterated as ‘th’.

    • ‘Look lower down the alphabet - theta perhaps, or even upsilon.’
    • ‘With these basic relationships in mind, let's now take a closer look at time value and the rate of time-value decay (represented by theta, from the Greek alphabet).’
    • ‘English borrowed the digraph th from Latin, where it served to transliterate Greek theta; th superseded other symbols for the dental fricative following the advent of printing.’
    1. 1.1Astronomy followed by Latin genitive The eighth star in a constellation.
      ‘Theta Draconis’
      • ‘Some of Ara's stars are very distant: both Gamma Arae and Theta Arae lie more than 1,000 light years away, but both of these stars are brilliant supergiants, and so are clearly visible to the naked eye of an observer on Earth.’
      • ‘It is 4.8° SSW of Theta Aurigae.’
    2. 1.2Chemistry as modifier Denoting a temperature at which a polymer solution behaves ideally as regards its osmotic pressure.
      • ‘We use equations derived from the blob theory to calculate the blob size and the theta temperature of star polymers.’
      • ‘For a given star polymer the theta temperature can be lower or higher than that of the corresponding linear polymer depending on the number and length of its branches.’

  • 1Temperature (especially in degrees Celsius).

  • 2A plane angle.

  • 3A polar coordinate.

    Often coupled with φ ( phi)