Square Root

In Word, type 221A in an equation, then press Alt+X. This is the documented Word workflow as of 2026. For a root symbol with a bar spanning several terms, use the equation editor's root structure rather than just inserting the character.

√ means the principal square root: for a nonnegative number, choose the nonnegative answer. So √9 means 3, not both 3 and −3.

Does √ apply to everything after it?

No—the bar or grouping marks its reach. The number or expression under the root is called the radicand.

A standalone text √ does not automatically stretch a bar over following characters. In plain text, put a longer radicand in parentheses; in a typeset equation, the overbar shows the same boundary.

Who invented the square root symbol?

The familiar notation developed in stages. These marks gave mathematicians a written way to indicate roots and their boundaries.

Leonardo of Pisa used an R-like square-root notation in 1220. Christoff Rudolff's radical appeared in 1525, following earlier dot-based notation; he also used extra dots to mark where a radical ended.

Albert Girard proposed placing a small root index at the opening in 1629. René Descartes added the overbar, also called a vinculum, in 1637, making the expression under the root visible.