Closed interval: specified end points are included.
Open interval: specified end points are not included.
Half-open = half-closed interval: one of the specified end point is included but not the other.
An interval is identified by specifying the end point values of the interval.
It may be written (for example) as something like:
This is an example of a closed interval which indicates that
As an alternative we might have:
which is an open interval which indicates that
A half-open interval might look like
...any value greater than but not equal to
...which would include