Surds are unresolved radicals, such as
square root of 2
cube root of 5
These are examples of surds that are irrational numbers, since they cannot be expressed as ratios of integers. On the other hand, some surds are not irrational numbers, such as
square root of 9
cube root of 8
since they can be expressed as the ratio of integers (in fact, these are exactly integers).
There are also irrational numbers that cannot be expressed as surds. These are transcendental numbers. Examples are
pi = 3.1415926535897932384....
e = 2.718281828...
hope this time i help