Tau — τ Greek Letter Symbol
τ
Tau — τ / Τ
19th letter of the Greek alphabet · pronounced /tɔː/ or /taʊ/
PhysicsMathematicsEngineeringMechanics
Copy symbol
τ
Lowercase tau
Τ
Uppercase Tau
Technical reference
| Unicode (lowercase) | U+03C4 |
| Unicode (uppercase) | U+03A4 |
| HTML entity | τ |
| HTML decimal | τ |
| LaTeX | \tau |
| Python / Unicode escape | \u03c4 |
| Alt code (Windows) | Alt + 964 |
Uses in science & engineering
Shear stress
Force per unit area acting parallel to a cross-section. Fundamental in structural and geotechnical engineering.
\(\tau = \frac{F}{A}\)
Torque
Rotational force about an axis. Used in mechanical and structural engineering.
\(\tau = r \times F\)
Time constant
Characterises the speed of response of a first-order dynamic system (RC circuits, thermal systems).
\(v(t) = V_0\left(1 – e^{-t/\tau}\right)\)
Tau (mathematics)
Alternative circle constant τ = 2π, used by some mathematicians as a more natural constant.
\(\tau = 2\pi \approx 6.2832\)
Proper time (relativity)
Time measured by a clock moving with an object, as opposed to coordinate time.
\(d\tau = dt\sqrt{1 – v^2/c^2}\)
Related symbols
How to insert in applications
Windows
Best option: copy from this page.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
Or press Win + . to open emoji & symbols panel.
Alt codes work only in Word/Notepad with NumLock on and English layout — not in browsers.
macOS
Press ⌃⌘Space → Character Viewer → search “tau”
Microsoft Word
Type 03c4 then press Alt+X
Google Docs
Insert → Special characters → search by name
Excel
Insert → Symbol → Subset: Greek → select symbol
LaTeX
Use in math mode: $ … $
Python
Use Unicode escape or chr()
HTML / CSS
Use HTML entity or decimal code