Number

Surd

An irrational root that cannot be simplified to a rational number, e.g. √2, √15.

Definition

A surd is a root of a number (usually a square root) whose value is irrational. Surds are kept in exact form rather than rounded. You can simplify, multiply and rationalise the denominator using surd rules.

Example

√12 simplifies to 2√3. √4 is NOT a surd because it equals 2 (rational).

Used in these topics

Surds →

Related terms

Rational number

A number you can write as a fraction p/q where p and q are integers and q ≠ 0.

Irrational number

A number that cannot be written as a fraction of two integers — its decimal goes on forever without repeating.

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