A number, whose value real and represents whole is defined as a natural number.
Natural numbers is a collection of numbers which represent real and complete quantities. It is originally used in counting objects, measuring whole quantities (not fractions) and labeling anything. Due to the use of these numbers in counting, the natural numbers are also called as counting numbers. It is a primary numeric system in real numbers.
The numbers (except zero) in Hindu-Arabic Numeral System are used as numbers of Natural numbers. The first number in natural number group is . Adding to first natural number gives second number. Add to second number and it returns third number. Thus, the group of natural numbers is formed in real number system.
Natural numbers are actually used for representing, the real things whose quantities are whole.
Let us understand it from two examples. Consider an apple, it is a whole apple (not a fraction). Therefore, it can be called one apple and it is written as apple in number system. Thus, natural number is used to represent it in numeric system.
Consider another example. Each thing is a star and it is whole. Therefore, natural numbers are used to count them. Hence, the number of stars is . In number system, it is written as stars.
The set of natural numbers can be expressed in mathematics by the concept of set theory. The set of natural numbers is denoted by the letter . The set of natural numbers of this group is written as follows.
Natural numbers is a collection of infinite numbers. Therefore, the set of natural numbers is known as infinite set.