What 𝕤 means
The formula or nearby definition tells you what it names.
Mathematicians commonly use double-struck type to mark sets. The surrounding notation gives this lowercase letter its particular role.
Why are the strokes doubled?
The style grew from a chalkboard workaround for bold type.
Chalk could not easily produce print-style bold, so mathematicians doubled one stroke. A math-typesetting article from 1988 describes this classroom technique as shaping printed forms. Fonts can draw the style with different outlines.
Part of the collection
Don't confuse it with
3
Cyrillic Small Letter Dze
Cyrillic small letter dze; looks identical to s in most fonts and is a classic spoof in web addresses.
ｓ
Fullwidth Latin Small Letter S
Full-width Latin letter used in East Asian text; looks like the plain s with extra width, and differs for search and passwords.
ſ
Latin Small Letter Long S
Old long-s letterform that looks like an f in some fonts; search tools may fold it to s, so results can differ.
Related characters
2
Questions people ask
1Why does 𝕤 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.
More like this
11
How to type or find 𝕤
- Also called
- blackboard-bold s · double-struck s
- Search it as
- blackboard bold s · double struck s · fancy s · outlined s
- Shows up in
- Anything that takes text · its shape is whatever your font draws
Windows (Word)
Windows
macOS
HTML
𝕤CSS
\1D564HTML or XML markup
Write
𝕤 in markup where the character should appear.Unicode NFKC text normalization
It folds 𝕤 to plain s; avoid it when a formula depends on the style distinction.
Codes and encoding1 code points
HTML decimal
𝕤
HTML hex
𝕤
CSS content
content: "\1D564";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%F0%9D%95%A4
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.