Greek Small Letter Sigma σ

The Greek Small 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+03C3 in the Universal Character Set.

Sigma is the eighteenth letter of the Greek alphabet and one of the most important in statistics and engineering. Lowercase sigma represents standard deviation, stress in mechanics, the Stefan-Boltzmann constant, and electrical conductivity. In quality management, sigma is central to Six Sigma methodology.

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 Small 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 sigma entity in statistics (standard deviation σ), physics (stress, conductivity), and quality management content (Six Sigma). It is one of the most commonly referenced Greek letters in business and engineering. The uppercase Σ is used for summation notation.