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Origin Adapted from Phoenician consonantal script, about the 8th century BCE
Tau is the nineteenth letter of the Greek alphabet, from the Phoenician taw, meaning mark or sign and originally drawn as a cross, and the ancestor of Latin T. It sounds the t, and its value in isopsephy is three hundred, placing it three hundredth in the numeral order. Because both its shape and its Semitic origin are a cross, Tau is an ancient symbol of the cross: the T-shaped tau cross, the crux commissa, is associated with the prophet Ezekiel and with Saint Anthony, and it was adopted by Saint Francis of Assisi, so that the Tau remains the emblem of the Franciscan order. In mathematics the number tau, about 6.28318, twice pi, has been proposed as a circle constant; in physics tau denotes a time constant, torque, and the tau lepton, and in biology the tau protein is central to Alzheimer research.
Facts
Origins
Origin PeriodAdapted from Phoenician consonantal script, about the 8th century BCE 1Tradition: The Greek alphabet and the Milesian numerals Origin PeriodEvery European alphabet descends from that decision 1Tradition: The Greek alphabet and the Milesian numerals Origin PeriodInnovation: wrote vowels with letters of their own 1Tradition: The Greek alphabet and the Milesian numerals Place of OriginPrecise place disputed: Al Mina, Cyprus, Crete, Euboea all argued for 1Tradition: The Greek alphabet and the Milesian numerals Place of OriginThe Aegean world, at a point of contact with Phoenician traders 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameAlpha, beta, gamma are aleph, bet, gimel: ox, house, camel 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameClearest evidence the alphabet was taken over, not invented 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameGreek letter names are borrowed Semitic words meaning nothing in Greek 1Tradition: The Greek alphabet and the Milesian numerals Sense of the Namemark or cross (from Phoenician taw) 1Tradition: The Greek alphabet and the Milesian numerals The pictographic sense is a modern reconstruction from the letter name rather than a meaning attested in the script's own period, and the atlas records that position elsewhere on this letter. The name itself is inherited; the picture behind it is inferred. Identity
Script TypeAn alphabet: each letter writes a single sound, consonant or vowel, inherited from Phoenician's twenty-two consonantal signs but repurposing several of them, for the first time in the alphabet's history, to write vowels outright. 1 PositionNineteenth of twenty-four in the Greek alphabet 1 Attributions
Associated SoundVoiceless dental stop t 1 Attestation
Meaning in the Attesting SourceIsopsephy (Greek gematria) attested in inscriptions and magical papyri 1Tradition: The Greek alphabet and the Milesian numerals Meaning in the Attesting SourceThe 27-sign series used three lost letters: digamma/stigma, koppa, sampi 1Tradition: The Greek alphabet and the Milesian numerals Meaning in the Attesting SourceThis atlas's 24 letters hold none of those three 1Tradition: The Greek alphabet and the Milesian numerals Learn More
Tau: The Greek Letter (Value 300), from Mark or Cross
Tau is the nineteenth Greek letter, from Phoenician taw ('mark'); its value is 300. Tau carries strong genuine symbolism: its capital shape is that of a cross (the crux commissa or 'Tau cross', also called Saint Anthony's cross), and it was linked from early times to the protective 'mark' of Ezekiel 9:4; Franciscans adopted the Tau as their emblem.
The Greek letters doubled as numerals in the Milesian (alphabetic) system, in which each letter carried a fixed value; the practice of summing a word's letters into a number, called isopsephy, is the Greek counterpart of Hebrew gematria and appears in inscriptions, the Greek Magical Papyri and early Christian texts. Tau's Phoenician ancestry places it in a borrowing whose exact point of contact, somewhere among Al Mina, Cyprus, Crete and Euboea in the Aegean world, is still disputed, though the borrowing itself, conventionally dated to around the 8th century BCE, is agreed to be the ancestor of every European alphabet still in use, including the Latin one covered elsewhere in this atlas.
The Greeks' own contribution was to give vowels dedicated letters of their own, something the consonant-only Phoenician script never did. Its isopsephy value of 300 belongs to the Milesian alphabetic numeral system, which also needed three further, otherwise obsolete letters, digamma (also called stigma), koppa and sampi, to cover every value from 1 up to 900; none of the three survives among the 24 letters in ordinary use today.
Tau in Modern Use
Tau's modern technical uses span physics, biology and a minority position in mathematics, none connected to the letter's ancient sound and numeral value, covered elsewhere in this atlas. Physicists named the tau lepton, a much heavier relative of the electron and the muon discovered in experiments at Stanford in 1975, directly after the letter, continuing the same naming pattern as the earlier muon, discussed elsewhere in this atlas; engineers and physicists also use lowercase tau for a time constant describing how quickly a system responds to change.
In biology and medicine, tau denotes a protein that stabilises the internal skeleton of nerve cells; abnormal tau protein forms tangles strongly associated with Alzheimer's disease and several related neurodegenerative disorders, making tau one of the most closely studied proteins in contemporary dementia research. A small but vocal minority of mathematicians has also proposed since 2010, in what its authors call the Tau Manifesto, replacing pi with a constant called tau, defined as twice pi, arguing it simplifies many formulas involving circles; the proposal has an informal following, marked by an annual Tau Day on June 28, but has not displaced pi in standard mathematical practice.
Cross-Tradition Connections
Derived from This
The Latin letter T descends from Greek Tau, reaching Latin through the Etruscan adaptation of a Western Greek alphabet. A straightforward continuation of shape, order and sound value.
Taken over into heavy native use, since Egyptian had a t of its own
Tverdo takes its shape from Greek tau and its numeral value of 300 from the same letter.
Why this is disputed. Glagolitic Tvrido is read as Greek Tau's counterpart in an alphabet Cyril modeled on Greek order and numeral values, but which theory explains where its rounded letterform actually came from is a live paleographic dispute. The mainstream palaeographic school, developed since Isaac Taylor's nineteenth century study, derives Glagolitic's ornamental shapes from medieval Greek cursive minuscule redesigned for Slavonic use. A rival idiographic school reads Glagolitic as substantially an original invention, its shapes built from basic forms such as the cross, circle and triangle rather than borrowed from any existing script, so this specific correspondence to Tau is accepted by one camp and denied by the other.
Related To
Roman T and Greek Tau continue the same Phoenician taw.
Samaritan Taaf and Greek Tau both continue the same Phoenician sign, and both write t. In the Semitic alphabets it is the last letter; in Greek the sequence carries on past it with the signs Greek added for itself.
Coptic Tau is the Greek tau, also read tav in Coptic Orthodox usage and used to build the feminine definite article; both carry the numeral value 300.
Greek Tau and Hebrew Tav are cognates. Both continue the same Phoenician sign, which is why both carry the numeral value 400 in their letter-number systems. A shared ancestor, not a borrowing in either direction. The Greek alphabet was adapted from the Phoenician abjad in the early first millennium BC, and the Hebrew square script descends from the same abjad through Aramaic.
Hebrew Tav and Greek Tau continue the same Phoenician taw; both carry the numeral value 400 in their letter-number systems.
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