Greek Small Letter Tau τ

The Greek Small Letter Tau character (τ) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference τ, the decimal numeric character reference τ, or the hexadecimal numeric reference τ. The character is assigned Unicode code point U+03C4 in the Universal Character Set.

Tau is the nineteenth letter of the Greek alphabet, representing torque in mechanics, the time constant in RC circuits, shear stress in materials science, and Kendall's tau in statistics. Some mathematicians advocate for tau (τ = 2π ≈ 6.28318) as a more natural circle constant than pi.

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 Tau character in your HTML documents, the named entity τ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form τ and hexadecimal form τ 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 tau entity in physics (torque τ, time constant), engineering (shear stress), statistics (Kendall's tau), and mathematical discussions about the tau vs. pi debate. It is essential for electrical engineering content involving time constants and circuit analysis.