τ

τ U+03C4, τ GREEK SMALL LETTER TAU ← σ Greek and Coptic υ →

τ

1. (physics) Torque.
2. (physics) Shear stress.
3. (physics) Optical depth.
   • 2006 August, Alexander V. Krivov, Artem G. Feofilov, Valeri V. Dikarev, “Search for the putative dust belts of Mars: The late 2007 opportunity”, in Planetary and Space Science, volume 54, numbers 9–10, →DOI, page 871:

     The first one was made by the Viking Orbiter 1 spacecraft in 1980 (Duxbury and Ocampo, 1988) and brought a negative result, setting the upper limit of the normal optical depth of the putative tori to ${\displaystyle \tau \lesssim 3\times 10^{-5}}$.

4. (mathematics, neologism) An irrational constant defined as the ratio of the circumference of a circle to its radius, equal to the radian measure of a full turn; approximately 6.283185307 (equal to 2π, or twice the value of π).
5. (physics) tauon
6. (Teutonista) a voiceless dental plosive (IPA ).
7. (UPA) A voiced coronal click consonant (dental ⟨τ̦⟩ = IPA ; cacuminal ⟨τ̣⟩ = IPA ).

• τ on Wikipedia.Wikipedia

Derived from its majuscule counterpart Τ.

τ • (t) (lowercase, uppercase Τ)

1. Lower-case tau (ταῦ), the 19th letter of the ancient Greek alphabet. It represented the voiceless unaspirated alveolar or dental plosive /t/. It is preceded by σ and followed by υ.

See also tau

• τ΄, ͵τ
• т, Т (Cyrillic)
• 𐍄 (Gothic)
• ⲧ, Ⲧ (Coptic)

• (Greek-script letters) Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω
• (non-Classical letters) Ϝ ϝ, Ͷ ͷ, Ͱ ͱ, Ϻ ϻ, Ϙ ϙ, Ͳ ͳ
• (punctuation) · ;
• (diacritics) ᾿ ῾ ◌́ ◌̀ ῀ ¨

τ • (t) (lowercase, uppercase Τ)

1. The lower case letter tau (ταυ), the 19th letter of the modern Greek alphabet.

• (Greek-script letters) Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, Ω ω
• (non-Classical letters) Ϝ ϝ, Ͷ ͷ, Ͱ ͱ, Ϻ ϻ, Ϙ ϙ, Ͳ ͳ
• (punctuation) · ;
• (diacritics) ᾿ ῾ ◌́ ◌̀ ῀ ¨
• τ΄
• ͵τ