Greek Small Letter Epsilon ε

The Greek Small Letter Epsilon character (ε) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference ε, the decimal numeric character reference ε, or the hexadecimal numeric reference ε. The character is assigned Unicode code point U+03B5 in the Universal Character Set.

Epsilon is the fifth letter of the Greek alphabet and represents arbitrarily small positive quantities in mathematical analysis. The famous epsilon-delta definition of limits is foundational to calculus. In physics, epsilon represents permittivity, strain, and the Levi-Civita symbol.

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 Epsilon character in your HTML documents, the named entity ε is generally the most readable choice for developers reviewing or maintaining source code. The decimal form ε and hexadecimal form ε 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 epsilon entity in calculus and analysis (ε-δ proofs), physics (permittivity ε₀), engineering (strain), and computer science (machine epsilon). It is essential for rigorous mathematical content and frequently appears in algorithm analysis for error bounds.