What 𝐔 means
It has no fixed value on its own. A variable is a letter used to name a quantity or object; the formula tells you what this bold U stands for and whether it differs from a plain U.
Why is it a separate character?
By 1999, mathematical and technical publishers used bold, italic, and other letter styles as distinct mathematical forms. A proposal that year from specialists in mathematical publishing sought to preserve those distinctions in plain text, where font-only styling could disappear.
Part of the collection
Don't confuse it with
4
Armenian Capital Letter Seh
Looks like a U in many fonts; a known spoof letter in web addresses.
Ｕ
Fullwidth Latin Capital Letter U
Fullwidth Latin capital U, wider than plain U. Used in East Asian input; a different code point that looks alike.
Union
Union sign, a math symbol. Looks like a cup-shaped U; common in pasted math text, not a letter.
Circled Latin Capital Letter U
Circled capital U, an enclosed styled letter. Bubble shape, not the bold math letter.
Related characters
1
Questions people ask
1Why does mathematical bold U show as a box?
The selected font may not contain this character’s glyph. An app may show a missing-character box, blank space, or fallback symbol; a supporting font can also draw it differently.
More like this
12
How to type or find 𝐔
- Search it as
- bold u · math bold u · unicode bold u · bold unicode letter
- Shows up in
- Anything that takes text · its shape is whatever your font draws
Windows (Word)
Windows
HTML
𝐔CSS
\1D414LaTeX math input
In LaTeX, a text-based math typesetting system, write \mathbf{U} inside a formula to produce a bold math letter.
Unicode hex input
In an editor with character-code input, enter hex 1D414 and run its conversion command; the shortcut depends on the app.
Codes and encoding1 code points
HTML decimal
𝐔
HTML hex
𝐔
CSS content
content: "\1D414";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%F0%9D%90%94
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.