Definition:Negative/Real Number

Definition
The negative real numbers are the set defined as:
 * $\R_{\le 0} := \left\{{x \in \R: x \le 0}\right\}$

That is, all the real numbers that are less than or equal to zero.

Also known as
In order to remove all confusion as to whether negative real number is intended to mean strictly negaive real number, the use of the term non-positive real number is often recommended instead.

The -specific notation $\R_{\le 0}$ is actually non-standard. The conventional symbols to denote this concept are $\R_-$ and $\R^-$, but these can be confused with the set $\left\{{x \in \R: x < 0}\right\}$.