Integers and fractions are collectively called rational numbers. Integer is a number like -3, -2,-1, 0, 1, 2,3, 10. All integers form an integer set, which is a number ring. In the integer system, zero and positive integers are collectively called natural numbers. -1, -2, -3, …, -n, …(n is a non-zero natural number) are negative integers. Positive integers, zero integers and negative integers form an integer system. Integers exclude decimals and fractions. Fraction indicates the fraction of one number to another, or the ratio of one event to all events. Divide the unit "1" into several parts on average, and the number representing such a part or parts is called a fraction. The numerator is above and the denominator is below. A rational number is a set of integers and fractions, and integers can also be regarded as fractions with a denominator of 1. The fractional part of a rational number is a finite or infinite cyclic number. Real numbers that are not rational numbers are called irrational numbers, that is, the fractional part of irrational numbers is infinite cyclic numbers. The set of rational numbers can be represented by the capital black orthographic symbol Q, but Q does not represent rational numbers. The set of rational numbers and rational numbers are two different concepts. The set of rational numbers is the set of all rational numbers, and rational numbers are all elements in the set of rational numbers. The source of rational nouns in extended data: in fact, this is a translation error. The word rational number comes from the west and is rational in English, but rational usually means "rational", so some scholars translate it into "rational number". However, this word comes from ancient Greece, and its root is ratio, which means "ratio, ratio". So the original meaning of this word is: a number that can be written as the ratio of two integers. In contrast, "irrational number" is a number that cannot be expressed as the ratio of two integers, but it is not unreasonable. Then if we know that rational numbers are actually "numbers that can be written as the ratio of two integers", we can easily understand the concept of rational numbers. Scores: 5/2, 5/3 and 5/4; Integers are special fractions, such as 5=5/ 1, 1=5/5.