tau

noun

1. 1

   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.

2. 2

   A Τ-shaped object or sign; a Saint Anthony's cross, sometimes regarded as a sacred symbol.

   Nor ſhall we take in the myſticall Tau, or the Croſſe of our bleſſed Saviour, which having in ſome deſcriptions an Empedon or croſſing foot-ſtay, made not one ſingle tranſverſion.

3. 3

   A Τ-shaped object or sign; a Saint Anthony's cross, sometimes regarded as a sacred symbol. A crosier with a Τ-shaped head.

4. 4

   The ankh symbol (☥).

5. 5

   Chiefly written τ: used to designate the nineteenth star (usually according to brightness) in a constellation.

6. 6

   A measurement of the sensitivity of the value of an option to changes in the implied volatility of the price of the underlying asset.

   (includes a list of coordinate terms)

7. 7

   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).

8. 8

   Variant of tawAlternative form of taw; the 22nd and last letter of many Semitic alphabets/abjads, including Phoenician, Aramaic, Hebrew, Syriac, and Arabic.

   In the Spanish translation of Sallust, by the Infant Don Gabriel in 1772, called the Infant Sallust, there is a curious dissertation by Father Perez Bayer on the resemblance between the ancient Hebrew and Phœnician alphabets, in which it is observed that the Hebrew Tau was written in pure Phœnician, […]

   The tau is both the 19ᵗʰ letter of the Greek alphabet, and also the 22ⁿᵈ letter of the Hebrew alphabet. In this context, the Hebrew tau or tav is more pertinent.

9. 9

   Variant of tau proteinEllipsis of tau protein (“a protein abundant especially in the neurons of the human central nervous system that stabilizes microtubules, and when misfolded is associated with forms of dementia such as Alzheimer's and Parkinson's diseases”).

   Quite what that job is remains obscure, but one theory is that it is to stabilise another protein called tau, which is supposed in turn to keep in shape the tubular ‘skeleton’ of a neuron.

10. 10

    Variant of tau lepton or tau particleChiefly written τ. Ellipsis of tau lepton or tau particle (“an unstable elementary particle which is a type of lepton, having a mass almost twice that of a proton, a negative charge, and a spin of ½; it decays into hadrons (usually pions) or other leptons, and neutrinos; a tauon”).

11. 11

    Variant of tau mesonhistoricalChiefly written τ. Ellipsis of tau meson, now known as a kaon.

Forms

plural

taus