négyzetgyökjel

The four-sided root symbol, known in Hungarian as "négyzetgyökjel," is a mathematical symbol used to denote the principal square root of a non-negative number. It is a radical symbol, originating from the Latin word "radix," meaning root. The symbol itself, $\sqrt{}$, visually represents a checkmark with a horizontal line extending from its top. This horizontal line indicates the extent of the radicand, the number or expression under the root.

The operation of finding the square root is the inverse of squaring a number. For example, the square root of 9 is 3 because $3^2 = 9$. The négyzetsgyökjel is specifically used for the principal or non-negative square root. If a number has two square roots (e.g., both 3 and -3 square to 9), the négyzetsgyökjel will only refer to the positive one, 3. To indicate the negative square root, one would place a negative sign before the symbol, such as $-\sqrt{9} = -3$.

The symbol's history is somewhat obscure, with various forms appearing in mathematical texts over centuries. Its current common form gained widespread acceptance in the 16th century. It is a fundamental symbol in algebra, geometry, and many areas of science and engineering, indispensable for solving equations and expressing mathematical relationships involving squares and their origins. The concept of square roots extends beyond real numbers to complex numbers, where the négyzetsgyökjel still applies, though the interpretation of "principal root" becomes more nuanced.