N-ary Summation Symbol
∑ is the N-ary summation symbol, commonly used to express sums over a sequence or index.
U+2211
The symbol “∑” (Unicode U+2211) is called the N-ary summation. It’s widely used in mathematics and STEM writing to show that many terms are added together. This page helps you copy it reliably and understand common ways to use it.
N-ary Summation Symbol Meaning
∑ (N-ary Summation) denotes summation across an index—meaning you add a sequence of terms that share a pattern. Typically, you pair it with an index and bounds, such as “∑_{i=1}^{n}” followed by an expression that depends on that index. The letter-like sigma shape helps readers quickly identify that the expression represents a total rather than a single value. While it’s most common in math notation, it also appears in formulas in technical documents, spreadsheets, and typeset writing to communicate aggregated calculations clearly.
Common uses
- •Writing mathematical formulas for total sums over an index range
- •Defining series and sequences in homework, notes, and textbooks
- •Documenting algorithms or data processing steps that add many values
- •Creating equation labels and captions for reports and presentations
- •Using Unicode math symbols in UI text, design mockups, and technical posts
Examples
∑ N-ary Summation Symbol (U+2211)
- ∑∑_{k=1}^{n} k
- ∑∑_{i=0}^{n} a_i
- ∑Total = ∑_{t=1}^{T} x_t
- ∑S = ∑_{m=1}^{M} f(m)
- ∑∑_{i=1}^{n} (b_i - \u00178_i)
Variations
Ready to copy
Technical codes
| Unicode | U+2211 | |
| HTML Entity | ∑ | |
| HTML Code | ∑ | |
| CSS | \2211 |
FAQ
What does the symbol ∑ mean?
It denotes summation (an N-ary sum), meaning you add multiple terms over an index or range.
How do I type or copy ∑ in Unicode?
Copy the character “∑”, or use Unicode code point U+2211 in your system/app that supports it.
What are the HTML and CSS escapes for ∑?
HTML entity: ∑. CSS escape: \\2211.
Can ∑ be used outside of math papers?
Yes. It’s often used in technical writing, UI text for aggregations, and design or social posts when referring to totals or formulas.