Infinity ∞

The Infinity 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+221E in the Universal Character Set.

The infinity symbol is a mathematical concept representing an unbounded quantity, depicted as a horizontal figure-eight (lemniscate). It appears in calculus limits, set theory, projective geometry, and philosophical discussions. The symbol was introduced by mathematician John Wallis in 1655 and has become one of the most widely recognized mathematical symbols.

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 Infinity 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 infinity symbol in mathematical limits (lim as x → ∞), set theory (countable vs. uncountable infinity), interval notation, and metaphorical usage in marketing or philosophical content. It is one of the few mathematical symbols that has achieved broad cultural recognition beyond mathematics.