Definition of epsilon in English:



  • 1The fifth letter of the Greek alphabet (Ε, ε), transliterated as ‘e.’

    1. 1.1[as modifier]Denoting the fifth in a series of items, categories, etc.
    2. 1.2Astronomy [followed by Latin genitive]The fifth star in a constellation.
      ‘Epsilon Carinae’
      • ‘The star Epsilon Eridani, 10 light years from Earth, was then found to have exactly the disc clumps predicted by the computer models.’
      • ‘This had just begun with Frank Drake's brief microwave observation of Epsilon Eridani and Tau-Ceti back in 1960 - Project Ozma.’
      • ‘It's a satellite base that they plan to put in orbit around Epsilon Draconis.’
      • ‘The most likely destinations are the stars closest to Earth, such as Alpha Centauri and Proxima Centauri, Tau Ceti, and Epsilon Eridani.’
      • ‘The University of Texas team found a planet similar in size to Jupiter about 10.5 light years away from Earth orbiting the star Epsilon Eridani, a star very similar to the sun.’

  • Permittivity.


Early 18th century: Greek, plain or simple E from psilos plain referring to the need to distinguish epsilon from the diphthong ai: in late Greek the two had the same pronunciation.