How to type Summation

∑ lives in the Mathematical Operators block (U+2200-U+22FF), the core set of mathematical and logical operators. Within Unicode it is classified as Sm, a mathematical symbol. Software may lay it out with the spacing an operator expects.

How to type ∑ in Microsoft Word and on a phone

In Microsoft Word, type 2211 and press Alt + X. Word reads the four characters before the cursor as a hex codepoint and replaces them, and pressing Alt + X again turns ∑ back into 2211, which is the quickest way to check what a character really is.

On a phone, neither iOS nor Android has a codepoint route. Copy ∑ from this page once, then add it as a text replacement (Settings, General, Keyboard on iOS) so a short abbreviation expands to it from then on.

What Summation is used for

In mathematical notation ∑ is a large operator: it takes limits above and below it in displayed maths and shrinks them to sub- and superscripts inline, which is why the same expression looks different in a paragraph and on its own line. That is the classification unicode-math gives it, and it is what decides how the symbol is set: $\sum$ in LaTeX, in maths mode rather than in a sentence.

Unicode publishes a second list of names for ∑ in CLDR, the keywords its own search data offers rather than the formal name, and they are n-ary summation and mathematics. Those words are what somebody looking for this character is liable to type when Summation is not the name they know it by, and the search on the symbol lists matches them as well as the Unicode name.

What ∑ gets confused with

Unicode's own confusables table, the one used to catch lookalike domain names, groups ∑ with Σ (U+03A3, Capital Sigma) and ⅀ (U+2140, Double-Struck N-Ary Summation). They are separate characters that render close enough to be mistaken for one another, so a search or a string comparison will separate them where your eye will not. If Summation is not matching where you expect it to, one of these is the usual reason.

What Unicode says about Summation

The standard recognises ∑ under another name as well: summation sign. That is a formal alias, not a nickname, which is why it turns up in other people's documentation for the same codepoint.

The code chart points from ∑ to Capital Sigma and double-struck n-ary summation (U+2140). These are the characters the standard thinks you might have meant instead, which makes them the ones worth checking when Summation looks nearly right but not quite.

How Summation behaves in software

∑ is East Asian Ambiguous: one column in a Western locale and two in a CJK one. That is why a table that lines up on your machine can break on somebody else's, with no change to the text at all. It carries no direction of its own, so in a line that mixes English with Arabic or Hebrew it takes the direction of the text around it rather than forcing one. It is a mirrored character: in right-to-left text it is drawn reversed, so it keeps pointing at what it pointed at.

What people ask about Summation

Every way to write Summation

Encodings and escapes for Summation (∑)

Form	Value
Codepoint	U+2211
Decimal	8721
UTF-8 bytes	E2 88 91
UTF-16 bytes	22 11
HTML entity	∑
HTML numeric	∑ or ∑
CSS	\2211
JavaScript	\u2211
Python	\u2211
URL-encoded	%E2%88%91
LaTeX, in maths mode	$\sum$
SVG	2211.svg · PNG (SIL Open Font License)

If ∑ arrives as ∑

One character has become three, which is what a three-byte UTF-8 sequence looks like when each byte is read separately: E2 88 91 read as Windows-1252 gives exactly ∑. The text is intact and the damage is in the reading, so setting the reader to UTF-8 restores it and retyping does not. A rectangle instead of the mojibake means the opposite: the encoding is right and the font has no glyph at U+2211, which for a character this far outside Latin-1 is common in older office fonts.