An irrational root of a rational number is called a surd.
When we can't simplify a number to remove a square root (or cube root etc) then it is a surd
1. √2 (square root of 2) can't be simplified further so it is a surd
√2 decimal form is 1.4142135...(etc) thus its a surd
2. √3 (square root of 3) can't be simplified further so it is a surd
√3 decimal form is 1.7320508...(etc) thus its a surd
3. 3√11 is a surd
4. 5√3 is a surd
[there are 2 types of surds>>>> like surds and unlike surds ]
hope my answer helped you......