Even number: refers to an integer with an even number at the end of a positive integer, such as 0, 2, 4, 6, 8, etc.

Singular number: refers to an integer ending in an odd number, such as 1, 3, 5, 7, 9, etc.

For example, for the number 10, because its last digit is 0 (even number), it is a double number; For the number 7, it is singular, because the number at the end is 7 (odd).

It should be noted that for negative integers, even numbers and odd numbers are also distinguished according to the characteristics of the last digits. For example,-10 is a negative integer, but its last digit is 0 (even number), so it is a double number; And -7 is a negative integer ending in 7 (odd number), so it is singular.

In addition, in some cases, positive and negative integers may be called "even number" and "singular number" respectively, but this is not the standard usage.

Even number and odd number are very basic concepts in mathematics, which are applied in many aspects, such as integer division, parity, cyclic decimal and so on. In daily life, we often need to distinguish even numbers from odd numbers, such as planning, statistics, calculation and many other aspects.

First of all, let's understand the definitions of even and singular. Even numbers refer to integers ending in even numbers, such as 0, 2, 4, 6, 8, etc. These numbers are divisible by 2, and the remainder is 0. Odd numbers refer to integers ending in odd numbers, such as 1, 3, 5, 7, 9, etc. The remainder of these numbers divided by 2 is not 0.

Besides positive integers, negative integers can be divided into even and odd numbers. For example,-10 is a negative integer, but its last digit is 0 (even number), so it is a double number; And -7 is a negative integer ending in 7 (odd number), so it is singular.

Even numbers and odd numbers have many applications in mathematics. For example, in integer division, if the remainder of one number divided by another number is 0, then this number is a double number; Otherwise it is singular. In addition, even number can be regarded as a special form of even number in parity. In addition, in cyclic decimals, if the decimal part of a decimal is cyclic, then this decimal is obtained by some operation from even numbers.

Besides the application in mathematics, even numbers and odd numbers are also common in daily life. For example, in many aspects such as planning, statistics and calculation, we need to distinguish even numbers from odd numbers. For example, when planning an activity, we need to determine whether the number of participants is even or odd, so as to arrange seats, group and so on.

In statistics, we need to distinguish whether the number of men and women is even or odd, so as to make reasonable arrangements and distribution. When calculating, we also need to distinguish whether the result of addition, subtraction, multiplication and division is even or odd, so as to make the next calculation or judge the accuracy of the result.

In a word, even and odd numbers are very basic concepts in mathematics, and they are applied in many aspects, such as integer division, parity, cyclic decimal and so on. In daily life, we often need to distinguish even numbers from odd numbers in order to carry out reasonable planning, statistics, calculation and other activities. By understanding and mastering the concepts and applications of even numbers and odd numbers, we can better understand and solve various problems in life.