What ∂ means
One variable changes; every other input stays frozen. In ∂f/∂x, you nudge x and keep the rest fixed. Ordinary d stands for total change, when the variables move together.
The curly d was dropped once, then revived
Condorcet used ∂ for partial differences in 1770, and Legendre wrote the modern ∂u/∂x form in 1786 before abandoning it. Carl Jacobi revived it in 1841, and his usage stuck. Earlier, Euler marked partial derivatives with parentheses instead.
Part of the collection
Don't confuse it with
3
Latin Small Letter D
Upright d means total or ordinary change; curled ∂ means change in one chosen variable.
Greek Small Letter Delta
Greek small delta has a closed loop with a hook on top and marks a small change or variation, not a partial derivative.
Latin Small Letter Eth
ð is the letter eth (Icelandic, Faroese, Old English) and has a crossbar through its stem. ∂ has no stroke and is a maths operator.
Related characters
3
Nabla
Nabla, the vector operator whose components are partial derivatives: ∇f lists ∂f/∂x, ∂f/∂y, ∂f/∂z.
Mathematical Italic Partial Differential
Mathematical italic partial differential, a separately encoded italic style of ∂ from the Mathematical Alphanumeric Symbols block.
Increment
The Laplace operator: ∆f adds up the unmixed second partials, ∂²f/∂x² + ∂²f/∂y² + ∂²f/∂z².
Combination ideas
5Partial derivative of f with respect to x.
Operator: differentiate in x, holding the other variables fixed.
Mixed second partial derivative of f.
The one-dimensional heat equation, with diffusivity set to 1.
The boundary of the region Ω.
Questions people ask
1Why does ∂ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
More like this
13
Collections with ∂
2
How to type or find ∂
- Also called
- partial · curly d · rounded d
- Search it as
- partial derivative · pde
- Shows up in
- Anything that takes text · its shape is whatever your font draws
Windows (Word)
Windows
HTML
∂CSS
\2202LaTeX
Write \partial in math mode, e.g. \frac{\partial f}{\partial x}.
Microsoft Word
Type 2202, then press AltX.
Codes and encoding1 code points
HTML decimal
∂
HTML hex
∂
CSS content
content: "\2202";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%88%82
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.