A closed interval is an interval that includes all of its limit points. If the endpoints of the interval
are finite numbers and , then the interval is denoted . If one of the endpoints is , then the interval still contains all of its limit
points (although not all of its *endpoints*), so and are also closed intervals, as is the interval .

# Closed Interval

## See also

Closed Ball, Closed Disk, Closed Set, Half-Closed Interval, Interval, Limit Point, Open Interval## Explore with Wolfram|Alpha

## References

Croft, H. T.; Falconer, K. J.; and Guy, R. K.*Unsolved Problems in Geometry.*New York: Springer-Verlag, p. 1, 1991.Gemignani, M. C.

*Elementary Topology.*New York: Dover, 1990.

## Referenced on Wolfram|Alpha

Closed Interval## Cite this as:

Weisstein, Eric W. "Closed Interval."
From *MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/ClosedInterval.html