tau
/taʊ/ noun, proper noun
Also a form of taw
Forms taus
- noun The letter Τ /τ in the Greek alphabet; being the nineteenth letter of the Classical and Modern Greek, and the twenty-first letter of the Old and Ancient Greek alphabets.
- noun A Τ-shaped object or sign; a Saint Anthony's cross, sometimes regarded as a sacred symbol.
- noun (Christianity) A crosier with a Τ-shaped head.
- noun The ankh symbol (☥).
- noun (astronomy) Chiefly written τ: used to designate the nineteenth star (usually according to brightness) in a constellation.
- noun (finance) A measurement of the sensitivity of the value of an option to changes in the implied volatility of the price of the underlying asset.
- noun (mathematics, neologism) Chiefly written τ: an irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its radius, equal to twice the value of pi (2π; approximately 6.2831853071).
- proper noun A surname from Chinese.
Synonyms
Etymology
From Middle English tau, taue, from Latin tau, from Ancient Greek ταῦ (taû) and Hebrew תָּו (tav).
Sense 7 was used by Joseph M. Lindenberg in 1991, and popularized by the American educator and entrepreneur Michael Hartl in a 2010 paper which explains that τ resembles π; and that τ is the Greek equivalent of t, the first letter of turn, and 2π corresponds to one turn of a circle with a radius of one unit.
Sense 8.1 (“ellipsis of tau lepton or tau particle”) was coined by the American physicist Martin Lewis Perl (1927–2014) after the first letter of Ancient Greek τρίτον (tríton, “third”), since the tau lepton or tauon was the third charged lepton discovered.
Variant of Tao.
Webster’s 1913
- noun The common American toadfish; --so called from a marking resembling the Greek letter tau (t). Tau cross. See Illust. 6, of Cross.
Etymology [Gr. tay^ the letter t (English T).]
Sources: Wiktionary · Webster’s 1913 — from the Wiktionary entry “tau”, CC BY-SA 4.0. Details