Greek Capital Letter Sigma Σ

The Greek Capital Letter Sigma character (Σ) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference Σ, the decimal numeric character reference Σ, or the hexadecimal numeric reference Σ. The character is assigned Unicode code point U+03A3 in the Universal Character Set.

Greek capital sigma (Σ) is one of the most important mathematical symbols, representing summation — the addition of a sequence of numbers. Its angular shape is distinct from any Latin letter. Sigma is central to mathematics, statistics, physics, and engineering. The Six Sigma quality methodology takes its name from this letter.

Greek letter entities are indispensable for scientific papers, engineering documentation, statistical analyses, and mathematical content published on the web. From physics equations using alpha and omega to statistical formulas featuring sigma and mu, these entities allow content authors to include Greek characters reliably without requiring specialized fonts or complex Unicode input methods on the keyboard.

When deciding how to encode the Greek Capital Letter Sigma character in your HTML documents, the named entity Σ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form Σ and hexadecimal form Σ are equally valid alternatives that work in contexts where named entities may not be supported, or when generating HTML output programmatically from server-side code. All three representations produce identical visual output in every modern web browser.

Use the capital sigma for summation notation (Σᵢ aᵢ), covariance matrices in statistics, and Six Sigma methodology references. It is one of the most frequently used Greek capitals in mathematical notation and is essential for any quantitative web content.