What ∐ means
It combines inputs while keeping each source distinct.
For sets, the coproduct forms a disjoint union: equal elements from different inputs stay as tagged copies. Category theory, which studies mathematical structures and the maps between them, generalizes this idea; its combined object is defined by how each input maps into it.
Formal math notation; the construction depends on the mathematical setting.
For sets, ∪ merges equal members; ∐ keeps tagged copies separate.
Don't confuse it with
2Questions 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 2210, 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 “n-ary coproduct”.
Linux
Ctrl+Shift+UType 2210, then Enter or Space.
HTML
∐CSS
\2210LaTeX
For LaTeX coprod, write `\coprod_{i\in I} X_i` in math mode. `\bigsqcup` is a different square-union operator.
Codes and encoding1 code points
HTML decimal
∐
HTML hex
∐
CSS content
content: "\2210";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%88%90
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.