What ⧞ means
It marked difference, paired against ∞ for identity.
A manuscript by the 17th-century mathematician Gottfried Wilhelm Leibniz labels ∞ “identity” and ⧞ “diversity,” or identity crossed out with a dagger-like mark. That explains Leibniz’s notation; it does not define every later formula.
Don't confuse it with
4Questions 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 29DE, 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 “infinity negated with vertical bar”.
Linux
Ctrl+Shift+UType 29de, then Enter or Space.
HTML
⧞CSS
\29DEMathML entity
The 2001 MathML 2 entity table lists `⧞` for ⧞.
Codes and encoding1 code points
HTML decimal
⧞
HTML hex
⧞
CSS content
content: "\29DE";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%A7%9E
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.