Every even number is followed by an odd number and every odd number is followed by an even number. What is the meaning ?

Solution:

As known, Even numbers are those numbers which are divisible by $2$, even number ends with $2,\ 4,\ 6,\ 8, 0...$.

Odd numbers are those numbers which are not divisible by $2$. Odd number ends with the digit $1,\ 3, 5,\ 7,\ 9...$

e.g. $1,\ 2,\ 3,\ 4,\ 5,\ 6,\ 7,\ 8,\ 9,\ 10,\ .......$

Here $2,\ 4,\ 6,\ 8,\ 10....$ are even numbers and followed by by $1,\ 3,\ 4,\ 5,\ 7,\ 9...$ which are odd numbers.

Similarly, odd numbers $1,\ 3,\ 5,\ 7,\ 9,\ .....$ are followed by even numbers  $2,\ 4,\ 6,\ 8,\ 10...$ respectively.