Definition:Real Interval/Unbounded without Endpoints

Definition
The unbounded (open) interval without endpoints is equal to the set of real numbers:


 * $\openint \gets \to = \R$

Also denoted as
The notation using $\infty$ is usual:

On the $\gets \cdots \to$ notation is preferred.

Also known as
Some sources refer to this as an open infinite (real) interval.

Also see

 * Definition:Open Real Interval
 * Definition:Closed Real Interval
 * Definition:Half-Open Real Interval
 * Definition:Unbounded Closed Real Interval
 * Definition:Unbounded Open Real Interval