tau

Fetched 2026-10-26 (cache).

Datamuse reports no synonyms or antonyms for this word.

Noun

1. {{senseid|en|Greek letter}} The [[letter#Noun|letter]] {{m|grc|Τ//τ|tr=-}} in the [[Greek#Adjective|Greek]] [[alphabet#Noun|alphabet]]; being the [[nineteenth]] letter of the [[Classical Greek|Classical]] and [[Modern Greek]], and the [[twenty-first]] letter of the [[Old Greek|Old]] and [[Ancient Greek]] alphabets.
2. {{alternative form of|en|taw}}; the 22nd and last letter of many [[Semitic]] [[alphabet]]s/[[abjad]]s, including [[Phoenician]], [[Aramaic]], [[Hebrew]], [[Syriac]]{{,}} and [[Arabic]].
3. {{senseid|en|tau-shaped object or sign}} A {{lang|grc|Τ}}-[[shaped#Adjective|shaped]] [[object#Noun|object]] or [[sign#Noun|sign]]; a [[Saint Anthony's cross]], sometimes [[regard#Verb|regarded]] as a [[sacred#Adjective|sacred]] [[symbol#Noun|symbol]].
4. The [[ankh]] symbol ([[☥]]).
5. {{lb|en|astronomy}} ''Chiefly [[write#Verb|written]]'' '''{{lang|grc|τ}}''': {{non-gloss|used to [[designate#Verb|designate]] the nineteenth [[star#Noun|star]] (usually according to [[brightness]]) in a [[constellation]].}}
6. {{lb|en|finance}} A [[measurement]] of the [[sensitivity]] of the [[value#Noun|value]] of an [[option#Noun|option]] to [[change#Noun|changes]] in the [[implied]] [[volatility]] of the [[price#Noun|price]] of the [[underlying#Adjective|underlying]] [[asset]].
7. {{senseid|en|constant}} {{lb|en|mathematics|neologism}} ''Chiefly written'' '''{{lang|grc|τ}}''': an [[irrational#Adjective|irrational]] and [[transcendental#Adjective|transcendental]] [[constant#Noun|constant]] [[represent]]ing the [[ratio]] of the [[circumference]] of a [[Euclidean]] [[circle#Noun|circle]] to its [[radius]], [[equal#Adjective|equal]] to [[twice]] the [[value#Noun|value]] of [[pi]] ([[2]]{{lang|grc|[[π]]}}; [[approximately]] 6.2831853071).
8. {{senseid|en|tau protein}} {{lb|en|neurology}} {{ellipsis of|en|tau protein|t=a [[protein]] [[abundant]] especially in the [[neuron]]s of the human [[central nervous system]] that stabilizes [[microtubule]]s, and when misfolded is associated with forms of [[dementia]] such as [[Alzheimer's]] and [[Parkinson's disease]]s}}.
9. {{lb|en|particle}} ''Chiefly written'' '''{{lang|grc|τ}}'''.

Proper noun

1. {{surname|en|from=Chinese}}.

Source: Wiktionary · CC BY-SA 4.0 (Wiktionary dump) · cached copy, not a rewrite.