Integral ∫

The Integral character (∫) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference ∫, the decimal numeric character reference ∫, or the hexadecimal numeric reference ∫. The character is assigned Unicode code point U+222B in the Universal Character Set.

The integral sign is the foundational symbol of integral calculus, representing the continuous sum of infinitesimal quantities. Developed by Leibniz from a stylized long 's' (for summa), it is used throughout physics, engineering, economics, and pure mathematics. The integral sign is one of the most important mathematical symbols on the web.

Mathematical HTML entities enable web authors to display proper mathematical notation without relying on images or specialized rendering libraries like MathJax or KaTeX. While complex equations and multi-line formulas may still benefit from dedicated math typesetting tools, individual symbols expressed as HTML entities render quickly, remain accessible to screen readers, and can be styled with CSS just like regular text content.

When deciding how to encode the Integral character in your HTML documents, the named entity ∫ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form ∫ and hexadecimal form ∫ 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 integral sign in calculus expressions, physics formulas, and engineering documentation. For complex integrals with limits, bounds, and differential notation, use a dedicated math rendering library. The HTML entity works well for simple inline references to integration.