What 𝛔 means
It marks sigma as a distinct bold mathematical symbol.
In an equation, bold weight can distinguish this quantity from plain σ. Some conventions use bold lowercase Greek letters for vectors, while others use bold italic; the formula’s definitions decide what this sigma represents.
MathML, a markup for web formulas, can also store plain σ with its mathvariant set to bold. The rendered style can match even though the character data differs.
Why can mathematical bold sigma become plain sigma?
Compatibility normalization can fold it into plain σ.
If text processing applies NFKC or NFKD normalization, 𝛔 becomes σ. That can merge two symbols a formula meant to distinguish.
Keep the original character when the difference matters, or use math markup that stores bold as a style.
Mathematical; bold marks a notational distinction, while the formula defines what sigma stands for.
Bold alone does not establish that it is a vector.
Part of the collection
Don't confuse it with
1
Questions people ask
1Why does 𝛔 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
10
How to type or find 𝛔
- Also called
- bold sigma
- Search it as
- math bold sigma · bold lowercase sigma · bold Greek sigma
- Shows up in
- Anything that takes text · its shape is whatever your font draws
𝛔\1D6D4𝛔.\u{1D6D4}.Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.