Simple number

A simple number is a number you can use for normal calculations.

Explanation

This is a vague concept. Today we call simple numbers, the real numbers.

This was done after the introduction of complex numbers, which play an important role in mathematics. These numbers were originally called imaginary numbers. Some strange names are centuries old and are still being used. That is part of our culture.

Warning

There are also so-called normal numbers. That is a mathematical name for numbers with properties that we find fairly "normal".