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Radical sign or symbol
A symbol √ used to indicate that a root is being taken - such as a square root.
See definition of root.

The bar length matters

The horizontal bar in the radical symbol tells how much of the expression is to be used.
In this expression: the bar stretches across the whole expression "p - q". So this means we subtract q from p, then find the square root of the result.

If it has only covered the 'p' like this: it would mean find the square root of p then subtract q from the result.

The bar acts like parentheses, telling you how to group items and the order of calculation.

The radical sign is a symbol that means "root of". The length of the horizontal bar is important. See note below. When used in an expression like the one above, the whole expression is called a radical.

Used in a radical expression

The three components of a radical expression are

Degree The number of times the radicand is multiplied by itself. 2 means square root, 3 means cube root. After that they are called the 4th root, 5th root and so on. If this is missing, it is assumed to be 2 - the square root.
Radical symbol The symbol that means "root of". The length of the horizontal bar is important. See note below.
Radicand The thing you are finding the root of.

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Other exponents and roots topics