A surd is when you have a number that is irrational or in other word, A number that its number cannot be square rooted e.g. A square root of 2,3,5 etc, on the other hand an indices are numbers that are cubed or squared for instance 3^3 ('3 cubed' or '3 to the power of 3') and 5^2 ('5 squared' or 5 'to the power' of 2) are example of numbers in index form.3^3 = 3x3x32^1 = 22^2 = 2x22^3 = 2x2x2etc.The ^2 and ^3 are known as indices. Indices are useful (for example they allow us to represent numbers in standard form) and have a number of properties.