[tou, taw for 1, 2, 4; tahv, tawv for 3]


the 19th letter of the Greek alphabet (T, τ).
the consonant sound represented by this letter.
Also tau·on [tou-on] /ˈtaʊ ɒn/. Physics. tau lepton.
Also called tau protein. Biochemistry. a protein that is an important component of nerve cells, helping to maintain their function and structure: in the brain, distortions in the protein’s molecular shape is associated with the onset of Alzheimer’s disease.

Origin of tau

1250–1300; Middle English < Latin < Greek taû < Semitic; cf. tav
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for tau

Contemporary Examples of tau

Historical Examples of tau

  • It is an embryonic form, and therefore inferior in rank to the Tau moth.

    Our Common Insects

    Alpheus Spring Packard

  • Now Ra-Molo had a brother who bore the name of Tau (the lion).


    Minnie Martin

  • The pastures of Tau through the mist; the mist is distinctly visible.

    A Tour Through The Pyrenees

    Hippolyte Adolphe Taine

  • It is noticeable that the Christian flag bears the Tau Cross.

  • This tau was unquestionably the emblem of life, and, therefore, of the greatest virtue.

    Evolution in Art

    Alfred C. Haddon

British Dictionary definitions for tau



the 19th letter in the Greek alphabet (Τ, τ), a consonant, transliterated as t

Word Origin for tau

C13: via Latin from Greek, of Semitic origin; see tav
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for tau

nineteenth letter of the Greek alphabet, from Hebrew taw, last letter of the Hebrew alphabet, literally "sign, mark."

Online Etymology Dictionary, © 2010 Douglas Harper

tau in Medicine



The 19th letter of the Greek alphabet.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.