Greek Small Letter Mu μ

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

Mu is the twelfth letter of the Greek alphabet and one of the most widely used Greek letters in science. It represents the population mean in statistics, the coefficient of friction in physics, the micro prefix (10⁻⁶) in SI units, and magnetic permeability. The micro sign (µ) is technically a separate Unicode character.

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 Mu character in your HTML documents, the named entity μ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form μ and hexadecimal form μ 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 mu entity in statistics (population mean μ), physics (friction μ, permeability μ₀), and when the mathematical mu is needed. For the SI micro prefix, the dedicated micro sign µ (U+00B5) is technically more correct, though the two characters are visually identical in most fonts.