*SET-U

English word origin

Etymology of tau

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

1 source sectionExtended source reportWiktionary original ↗
In this entry · 1 source sections

The source etymologies

Wiktionary via Kaikki / Wiktextract

The source reports below are imported and unreviewed by *SET-U. Separate numbered origins and differing source variants are preserved; agreement within this extraction is not independent corroboration.

Unnumbered source etymology

Original entry ↗
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. · Alternative form of taw; the 22nd and last letter of many Semitic alphabets/abjads, including Phoenician, Aramaic, Hebrew, Syriac, and Arabic. · A Τ-shaped object or sign; a Saint Anthony's cross, sometimes regarded as a sacred symbol. · A crosier with a Τ-shaped head.

Selected source glosses provide context, not a complete modern definition inventory

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.

Relationships mentioned by the source

These are extracted mentions, not a timeline or a verified sequence of immediate parents.

  • Inherited-form mentiontauenm
  • Derivation mentiontaula
  • Derivation mentionταῦgrc
  • Derivation mentionתָּוhe

This page abbreviates 7 auxiliary source items. The etymology narrative is not shortened. Omission counts are available in the audit fields below; consult the original for complete auxiliary material.

Inspect preserved source fields

Raw extraction fields are retained for auditing. Their order does not establish ancestry.

{
  "templates": [
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "!",
      "args": {},
      "expansion": "|"
    },
    {
      "name": "sequence box",
      "args": {
        "title": "Ancient Greek alphabet",
        "previous": "←\n sigma",
        "next": "→\n upsilon",
        "current": "",
        "text": "<big>Τ τ </big>\nAncient Greek: ταῦ",
        "footer": "Wikipedia article on tau"
      },
      "expansion": ""
    },
    {
      "name": "letter_disp2",
      "args": {
        "1": "sigma",
        "2": "",
        "3": "upsilon",
        "4": "ταῦ",
        "5": "Τ",
        "6": "τ"
      },
      "expansion": ""
    },
    {
      "name": "senseno",
      "args": {
        "1": "en",
        "2": "tau-shaped object or sign"
      },
      "expansion": "sense 3"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "π"
      },
      "expansion": "π"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "senseno",
      "args": {
        "1": "en",
        "2": "constant"
      },
      "expansion": "sense 7"
    },
    {
      "name": "senseno",
      "args": {
        "1": "en",
        "2": "tau protein"
      },
      "expansion": "sense 8"
    },
    {
      "name": "inh",
      "args": {
        "1": "en",
        "2": "enm",
        "3": "tau"
      },
      "expansion": "Middle English tau"
    },
    {
      "name": "der",
      "args": {
        "1": "en",
        "2": "la",
        "3": "tau"
      },
      "expansion": "Latin tau"
    },
    {
      "name": "der",
      "args": {
        "1": "en",
        "2": "grc",
        "3": "ταῦ"
      },
      "expansion": "Ancient Greek ταῦ (taû)"
    },
    {
      "name": "der",
      "args": {
        "1": "en",
        "2": "he",
        "3": "תָּו",
        "tr": "tav"
      },
      "expansion": "Hebrew תָּו (tav)"
    },
    {
      "name": "senseno",
      "args": {
        "1": "en",
        "2": "constant",
        "cap": "yes"
      },
      "expansion": "Sense 7"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "π"
      },
      "expansion": "π"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "π"
      },
      "expansion": "π"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τ"
      },
      "expansion": "τ"
    },
    {
      "name": "coinage",
      "args": {
        "1": "en",
        "2": "Martin Lewis Perl",
        "nat": "the American",
        "occ": "physicist",
        "nobycat": "1",
        "nocap": "1"
      },
      "expansion": "coined by the American physicist Martin Lewis Perl"
    },
    {
      "name": "noncog",
      "args": {
        "1": "grc",
        "2": "τρίτον",
        "t": "third"
      },
      "expansion": "Ancient Greek τρίτον (tríton, “third”)"
    },
    {
      "name": "lang",
      "args": {
        "1": "grc",
        "2": "τριτον"
      },
      "expansion": "τριτον"
    }
  ],
  "links": [
    [
      "tau",
      "tau#Middle_English"
    ],
    [
      "taue",
      "taue#Middle_English"
    ],
    [
      "tau",
      "tau#Latin"
    ],
    [
      "ταῦ",
      "ταῦ#Ancient_Greek"
    ],
    [
      "תָּו",
      "תו#Hebrew"
    ],
    [
      "t",
      "t#English"
    ],
    [
      "turn",
      "turn#English"
    ],
    [
      "τρίτον",
      "τρίτον#Ancient_Greek"
    ]
  ],
  "references": [],
  "descendants": [],
  "lexical": [
    {
      "pos": "noun",
      "glosses": [
        "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.",
        "Alternative form of taw; the 22nd and last letter of many Semitic alphabets/abjads, including Phoenician, Aramaic, Hebrew, Syriac, and Arabic.",
        "A Τ-shaped object or sign; a Saint Anthony's cross, sometimes regarded as a sacred symbol.",
        "A crosier with a Τ-shaped head."
      ],
      "tags": [
        "alt-of",
        "alternative"
      ],
      "recordId": "0583b925b572b5db1c86a025ea4d182272cf98ed594bc843fd4a5f5b201ba398",
      "rawRecordSha256": "da9330ee0d57d6b12a403bd106f5c4f7076665ad84cb43517fb35a7d2c466b52",
      "sourceRecordOrdinal": 152545
    }
  ],
  "omittedAuxiliaryFields": {
    "templates": 0,
    "links": 0,
    "references": 0,
    "descendants": 0,
    "lexicalRecords": 0,
    "lexicalSenses": 7,
    "glosses": 0
  }
}

Where this record stops

This page does not supply an independently verified sound-change sequence, first-use manuscript or complete family tree unless a cited analysis explicitly establishes one. Missing detail here is a limit of this record—not a claim that humanity knows nothing more.

An older meaning does not determine what a word must mean today. Follow the sources, preserve disagreements, and keep ancestry separate from interpretation.

Contribute located evidence for tau →

Source and snapshot

Imported from Wiktionary contributors; extracted by Tatu Ylonen / Wiktextract / Kaikki.org. Selected fields are reformatted and grouped; wording, source identity and etymology sections are retained. CC-BY-SA-4.0 applies to the imported source material.

Dump: 2026-10-01 · Extracted: 2026-10-30. These are snapshot dates, not the word’s first attestation or the page’s revision date.

Source entry and bibliography ↗Wiktionary revision history ↗Acquisition and rights ledger
Machine-source provenance
Source SHA-256
5ff2c072f8099f2d2ce484bd6957bf179f046d2ad37bc36555edf8bb84cb5291
Import run
73216b9a9b78ed3830994bf853103716f5a4dc57099e371e9f8fdc468facca26
Permanent entry ID
w-dGF1