α
Alpha — α / Α
1st letter of the Greek alphabet · pronounced /ˈælfə/
Physics
Mathematics
Chemistry
Engineering
Copy symbol
α
Lowercase alpha
Α
Uppercase Alpha
Technical reference
| Unicode (lowercase) | U+03B1 |
| Unicode (uppercase) | U+0391 |
| HTML entity | α |
| HTML decimal | α |
| LaTeX | \alpha |
| Python / Unicode escape | \u03b1 |
| Alt code (Windows) | Alt + 945 |
Uses in science & engineering
Thermal expansion coefficient
Describes how a material’s length or volume changes with temperature. Used in structural engineering to account for thermal movement in bridges, rails, and pipelines.
\(\Delta L = \alpha \cdot L_0 \cdot \Delta T\)
Angular acceleration
Rate of change of angular velocity in rotational dynamics. Relates torque to the moment of inertia of a rotating body.
\(\tau = I \cdot \alpha\)
Fine-structure constant
Fundamental dimensionless constant of electromagnetism, characterising the strength of the electromagnetic interaction. Approximately equal to 1/137.
\(\alpha = \frac{e^2}{4\pi\varepsilon_0 \hbar c} \approx \frac{1}{137}\)
Alpha particle (nuclear physics)
A helium-4 nucleus emitted during radioactive alpha decay. Used in radiation physics and nuclear engineering.
\(^{238}_{92}\text{U} \;\rightarrow\; ^{234}_{90}\text{Th} + \,^{4}_{2}\text{He}\;(\alpha)\)
Attenuation coefficient
Describes the reduction of signal intensity or wave amplitude as it travels through a medium. Common in acoustics, optics, and telecommunications.
\(I(x) = I_0 \cdot e^{-\alpha x}\)
Significance level (statistics)
The probability threshold below which the null hypothesis is rejected. Typically set to 0.05 (5%) in engineering and scientific research.
\(\alpha = 0.05\)
Related symbols
How to insert in applications
Windows
Best option: copy from this page.
Or press Win + . to open emoji & symbols panel.
Alt+945 on numpad works only in Word/Notepad with NumLock on and English layout — not in browsers.
Or press Win + . to open emoji & symbols panel.
Alt+945 on numpad works only in Word/Notepad with NumLock on and English layout — not in browsers.
macOS
Press ⌃⌘Space → Character Viewer → search “alpha”
Microsoft Word
Type 03b1 then press Alt+X
Google Docs
Insert → Special characters → search “alpha”
Excel
Insert → Symbol → Subset: Greek → select α
LaTeX
$\alpha$ in math mode
Python
“\u03b1” or chr(945)
HTML / CSS
α or α