Natural numbers:- The numbers 1 , 2 , 3 . . . which we use for counting are known as natural numbers.

Whole numbers:- If we add the number zero to the collection of natural numbers, we get whole numbers. Thus 0 , 1 , 2 , 3 . . . . form the collections of whole numbers.

Predecessor :- A number that comes before the given number.                           Eg:  the predecessor of 12 is 11.

Successor:- A number that  comes after a given number.                                        Eg:  the successor of 14 is 15.