What 𝐛 means
The formula supplies its meaning.
A bold b can mark a vector (an object with components) in some traditions.
A documented turning point came in 1901: E. B. Wilson's textbook Vector Analysis popularized Clarendon, a heavy typeface, for vectors against scalar letters (single values). In 1921, mathematician Hermann Weyl used bold x for a vector and plain xᵢ for one component.
What it means when someone sends it to you
2 readingsIn an undefined formula
The author's notation supplies 𝐛's role.
In a stylized social post
By 2025, math-bold letters also served as faux-bold.
Don't confuse it with
1Questions people ask
1Why does 𝐛 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 𝐛
Windows (Word)
Alt+XType 1D41B, then Alt+X to get 𝐛.
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 bold small b”.
Linux
Ctrl+Shift+UType 1d41b, then Enter or Space.
HTML
𝐛CSS
\1D41BWord for Windows
To type 𝐛 in Word for Windows, enter 1D41B (without U+) and press Alt+X. As of 2026, this shortcut is specific to Word.
Codes and encoding1 code points
HTML decimal
𝐛
HTML hex
𝐛
CSS content
content: "\1D41B";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%F0%9D%90%9B
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.