What ⅀ means
“N-ary” means the operator applies to a list of terms; “double-struck” names its style. Leibniz used to stand for sums in a manuscript in 1675. Euler’s use of the Greek capital sigma Σ for summation appears in 1755. Unicode records show that in 2001 the proposed name changed from “double-struck capital sigma” to “double-struck n-ary summation.”
Part of the collection
Don't confuse it with
3
Greek Capital Letter Sigma
Greek capital letter Sigma, a letter rather than a maths operator. It looks alike in many fonts but is a different character.
Latin Capital Letter Esh
Latin capital letter Esh, used in phonetic writing. Its shape resembles Σ and ∑, but it is a Latin letter.
𝚺
Mathematical Bold Capital Sigma
Bold Greek capital Sigma from the maths block. A styled copy with its own code point, heavier than Σ.
Related characters
1
Questions people ask
1Why does ⅀ 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 ⅀
- Also called
- double-struck sigma · blackboard-bold sum
- Search it as
- sum symbol · n-ary sum · math sigma
- Shows up in
- Anything that takes text · its shape is whatever your font draws
Windows (Word)
Windows
HTML
⅀CSS
\2140LaTeX
In XeLaTeX or LuaLaTeX, use unicode-math and a math font that supports it;
\mathbb{\sum} requests the double-struck sum form.Codes and encoding1 code points
HTML decimal
⅀
HTML hex
⅀
CSS content
content: "\2140";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%85%80
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.