What is the difference between rational and irrational numbers?
Irrational numbers cannot be expressed exactly by the ratio of two integers. Rational numbers can be. Irrational numbers in decimal form are infinite and non-repeating. We can know as many digits of them as we are willing to compute, but we cannot know their exact value. Rational numbers are finite or repeating. Their exact value can be written using a finite number of digits. When we want to indicate the exact value of an irrational number, we usually use a symbol.