What ⊛ means
The surrounding notation defines the operation.
One signal-processing use is circular convolution. Check the formula’s key or nearby definition to tell whether that is intended here; the glyph alone does not identify the operation.
Don't confuse it with
4Combination ideas
1Circular convolution of f and g, when the surrounding notation defines ⊛ that way.
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.
How to type ⊛
Windows (Word)
Alt+XType 229B, then Alt+X to get ⊛.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “circled asterisk operator”.
Linux
Ctrl+Shift+UType 229b, then Enter or Space.
HTML
⊛CSS
\229BJulia 1.x REPL
In the Julia 1.x REPL (its interactive prompt), type `\circledast` and press Tab.
Codes and encoding1 code points
HTML decimal
⊛
HTML hex
⊛
CSS content
content: "\229B";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%8A%9B
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.