What 𝓊 means
It marks a script-style mathematical u.
The surrounding formula defines its value; there is no universal quantity called script u. Within an equation, 𝓊 and plain u can name different symbols.
Unicode's mathematical script alphabet completes a smaller set of script-shaped letters that older computer text standards already contained. Software that applies NFKC normalization (a way to standardize text) turns 𝓊 into u, erasing the script distinction.
Don't confuse it with
1Questions people ask
1Why does 𝓊 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 𝓊
Windows (Word)
Alt+XType 1D4CA, then Alt+X to get 𝓊.
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 “mathematical script small u”.
Linux
Ctrl+Shift+UType 1d4ca, then Enter or Space.
HTML
𝓊CSS
\1D4CACodes and encoding1 code points
HTML decimal
𝓊
HTML hex
𝓊
CSS content
content: "\1D4CA";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%F0%9D%93%8A
1
On screen
1
Code points
2
JS .length
4
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.