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The Collaborative International Dictionary

Tau \Tau\ (tou), n. [Gr. tay^.] The nineteenth letter ([Tau], [tau]) of the Greek alphabet, equivalent to English t.


Tau \Tau\, n. [Gr. tay^ the letter [tau] (English T).] (Zo["o]l.) The common American toadfish; -- so called from a marking resembling the Greek letter tau ([tau]).

Tau cross. See Illust. 6, of Cross.

Douglas Harper's Etymology Dictionary

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


n. 1 The name of the letter Τ/τ in the Greek, Hebrew and ancient Semitic alphabets, being the nineteenth letter of the Classical Greek and Modern Greek, the twenty-first letter of Old Greek and Ancient Greek Greek. 2 A (lang grc Τ)-shaped sign or structure; a St. Anthony's cross, sometimes considered as a sacred symbol. 3 (label en particle dated) A tau meson, now usually known as a kaon. 4 (label en particle) An unstable heavy lepton, which decays into a muon or electron; a tauon. 5 (label en biology) A type of protein that stabilizes microtubules in the human central nervous system, failures of which are associated with forms of dementia. 6 (label en mathematics neologism) A constant equal to twice the value of pi; often written τ.


n. the 19th letter of the Greek alphabet


Tau (uppercase Τ, lowercase τ; ) is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.

The name in English is pronounced or , but in modern Greek it is . This is because the pronunciation of the combination of Greek letters αυ has changed from ancient to modern times from one of to either or , depending on what follows (see Greek orthography).

Tau was derived from the Phoenician letter taw (????). Letters that arose from tau include Roman T and Cyrillic Te (Т, т).

The letter occupies the Unicode slots U+03C4 (lowercase) and U+03A4 (uppercase). In HTML, they can be produced with named entities (τ and Τ), decimal references (τ and Τ), or hexadecimal references (τ and Τ).

Tau (particle)

The tau (τ), also called the tau lepton, tau particle, or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of . Together with the electron, the muon, and the three neutrinos, it is a lepton. Like all elementary particles with half-integral spin, the tau has a corresponding antiparticle of opposite charge but equal mass and spin, which in the tau's case is the antitau (also called the positive tau). Tau particles are denoted by and the antitau by .

Tau leptons have a lifetime of and a mass of (compared to for muons and for electrons). Since their interactions are very similar to those of the electron, a tau can be thought of as a much heavier version of the electron. Because of their greater mass, tau particles do not emit as much bremsstrahlung radiation as electrons; consequently they are potentially highly penetrating, much more so than electrons. However, because of their short lifetime, the range of the tau is mainly set by their decay length, which is too small for bremsstrahlung to be noticeable: their penetrating power appears only at ultra high energy (above PeV energies).

As with the case of the other charged leptons, the tau has an associated tau neutrino, denoted by .

Tau (mythology)

Tau is the name of an evil spirit in Guaraní mythology. Although Tau is not quite synonymous with the Devil in Christian beliefs, for example, he was sometimes referred to as The Evil Spirit and as such may have been a personification of evil itself. Tau was created along with his opposite, Angatupyry, by the supreme god of the Guaraní creation myth, Tupã, and was left with humanity on Earth.

Tau (Warhammer 40,000)

In the fictional setting of Warhammer 40,000, the Tau are a race and a playable army in the tabletop miniatures wargame.

The Tau rule a small interstellar empire on the very fringe of Imperium space. They are a relatively new power on the galactic scene. The Tau dream of uniting the races of the galaxy under their benevolent rule (by force if necessary). The Tau already rule a number of client races, including some annexed human worlds.

Tau (disambiguation)

Tau ,Τ or τ, is the 19th letter of the Greek alphabet.

Tau may also refer to:

Tau (Warhammer 40000)
  1. Redirect Tau (Warhammer 40,000)
Tau (water)

Tau is a British brand of still and sparkling bottled water.

Tau went on sale in 2003, and is available in 750ml (25 fl oz) or 330ml (11 fl oz) bottles. It is sold by the company which produces Tŷ Nant mineral water, who drilled a new borehole into their spring in Llanon, Wales, from which to draw water for their Tau range. Sales for the product were "excellent" in its first year, with main buyers being restaurants and hotels. The product is not available through retail outlets.

"Tau" is a Welsh word meaning "to be silent".


Tău may refer to several villages in Romania:

  • Tău, a village in Roșia de Secaș Commune, Alba County
  • Tău, a village in Zau de Câmpie Commune, Mureş County
Tau (1/3)

Tau is a public artwork by American artist Tony Smith, located on the urban campus of Hunter College, in New York City, New York, United State of America. Fascinated by mathematics, biology and crystals, Smith designed Tau with geometry at its root.

Tau (sculpture)

Tau, by American sculptor Tony Smith, was designed in the early 1960s. It is 14’ high x 12’ wide x 12’ deep, and made from black painted steel. Its title refers to the Greek letter 'T', which also describes the shape of the sculpture. Fascinated by mathematics, biology and crystals, Smith designed Tau with geometry at its root. There are two extant versions of the large sculpture: Tau (AP), and Tau (1/3).

TAU (spacecraft)

TAU (Thousand Astronomical Units) was a proposed unmanned space probe to a distance of one thousand astronomical units (1000 AU) from the Earth and Sun by NASA/JPL in 1987 using tested technology. One scientific purpose would be to measure the distance to other stars via stellar parallax. Studies continued into 1990, working with a launch in the 2005-2010 timeframe.

It was a proposed nuclear electric rocket spacecraft that used a 1 MW fission reactor and an ion drive with a burn time of about 10 years and reach a distance of 1000 AU in 50 years. The primary goal of the mission was to improve parallax measurements of the distances to stars inside and outside the Milky Way, with secondary goals being the study of the heliopause, measurements of conditions in the interstellar medium, and (via communications with Earth) tests of general relativity.

One of the tasks envisioned for TAU would be a flyby of Pluto. A Pluto flyby was achieved in 2015 by the New Frontiers program mission New Horizons.

Some of the instruments proposed for the design included 1.5-meter telescope for observations and a 1-meter telescope for laser communication with Earth.

After launch it would accelerate to about 106 km/s (about 22.4 AU/year) over 10 years, using xenon as propellant and a nuclear fission reactor for power.

Tău (Negură Bunget album)

Tău is the sixth studio album by Negură Bunget, released on February 27, 2015, by Lupus Lounge, a sublabel of Prophecy Productions.

When it was first announced in 2013, the album was listed as the first part of a planned "Transilvanian Trilogy".

Tau (rapper)

Piotr Kowalczyk (born June 25, 1986), better known under his stage nameTau, and formerly as Medium, is a Polish rapper, vocalist, beatboxer and hip-hop producer. In 2008, he released his underground debut album Seans spirytystyczny (Séance) under the name Medium. His next underground album Alternatywne źródło energii (Alternative Energy Source) was released in 2010, which helped Medium to be spotted by Marcin "Tytus" Grabski, CEO of Asfalt Records, who offered him a contract.

On November 22, 2011, Tau released his official debut album (performing as Medium) titled Teoria równoległych wszechświatów (The Theory of Parallel Universes), which, despite slight promotion, sold over eight thousand copies in Poland.

In 2012 Tau announced that he had converted to Christianity. A few months later he released his second album Graal (Holy Grail). The album was highly criticized by many reviewers due to its radical lyrics. In 2013, Medium and producer Galus formed a one-album-group Egzegeza. The album Księga słów (The Book of Words) was released on June 28, 2013 in a limited amount of copies.

On December 6, 2013, Medium announced that he had changed his pseudonym to Tau due to the fact that his name Medium may have been seen as connected to mediumship practice, which is in opposition to Christian philosophy. A few days later, on December 13, 2013, he declared that he left Asfalt Records in order to form his own label, Bozon Records.

On December 3, 2014, Tau released his first studio album under his new name, titled Remedium. The album peaked at #4 on the OLiS chart, having sold over fifteen thousand copies the album went gold.

On August 10, 2015, Tau posted a picture on his Facebook profile with a caption that he had finished making a new album. A few days later he said that it is almost sure that the album would be released in November 2015. On October 21, 2015, Tau revealed that his new project was to be titled Restaurator and it was going to be released on December 15, 2015.

Usage examples of "tau".

He thought about the stars passing by his window as if they were friends: Hamal, of course, and Menkar, and the sprinkling of tau stars, omi tau, xi tau and f tau, then Aldebaran and Algol, and Betelgeuse, who faded last in the lightening sky.

They talked about Ben Suc and Cu Chi, and Nha Trang, Bien Hoa, Long Binh, Hue, and Vung Tau where she and Bill had spent their first weekend.

By the Tau Cross the Cabalists expressed the number 10, a perfect number, denoting Heaven, and the Pythagorean Tetractys, or incommunicable name of God.

The beauty of this special nightfall filled Tau with peace, marred only by brilliant fireballs and the thunder of explosions nearby.

Pauli, typically provocative, said that Richard Tauber, the singer from the Metropole Theatre, would be much better in the role of Frederick the Great.

An area of the brain, apparently located near the so-called pineal eye, responds directly to unshielded Tau influence, and there is evidence that certain aspects of Tau are mutually responsive to strong psychic states.

Following his daily route to work, Tau stepped off the southbound Moffett Field slidewalk onto the cracked asphalt of King Road.

Crux Ansata, a Tau cross with a circle over it, means life-giving, 290-u.

The beach at Vung Tau, once the foundation of our union, has been replaced by a night on Yen Phu Street in Binh Khoi, and no edifice built upon such imperfect stone could be other than cracked and deficient.

I put it to you, Dr Brevis, that this is a remarkable record for one who claims very little knowledge of Tau techniques.

When conditions had stabilized and the Tau image remained unchanged, Brevis left the blister and went to the control room where the activity was now centred.

Veyitkaddash, Shemay rabbah And so it was that, twenty-one years after it had died in Riga, a major of paratroops of the Army of Israel, standing on a hill in the Promised Land, finally said Kaddish for the soul of Salomon Tauber.

Cleopatra considered the old woman to be the incarnation of Kerana, mother of the seven evil children of Tau, was reason enough to be concerned.

I look around the room at the assorted Tau Phis, wondering which one is Doug.

But this time the fear and tears in his voice cause his fellow Tau Phis to turn around to look.