−1

In mathematics, −1 (called negative one or minus one) is a special number. It is the number you add to 1 to get 0. This makes it the additive inverse of 1, which means it "cancels out" the value of 1 when you add them together.

Negative one is an integer, which means it is a whole number, but it is not a positive number. It sits between negative two (−2) and 0 on the number line. This number is very important in many areas of math because it helps us understand how numbers work when we are dealing with subtraction and directions.

In mathematics

Multiplying a number by −1 changes the number’s sign. For example, multiplying 5 by −1 gives −5. This works for any number and can be shown using basic math rules.

The square of −1, which means multiplying −1 by itself, equals 1. This is why multiplying two negative numbers together gives a positive result. In more advanced math, there are numbers whose square equals −1, but these are not regular numbers that we use in everyday calculations.