Algebra: Real numbers, Irrational numbers, etc

This module describes the concept of a real number. A vague, touchy feely definition of a real number is that a real number is a (signed) distance from a zero to any point on the number line:



Not needed for school students: the more strict definition of a real number, used by mathematicians, is that in the world of real numbers, any set of numbers that is limited from above, has a least upper bound that is a real number. See this article for details.
Some real numbers are integers (1, -2, 0, 0), some are rational (, 4, ). Some numbers are irrational. "Most" numbers are irrational, although in school you mostly deal with rational numbers, since they are easier.