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An interval is a set of real numbers that includes all real numbers between one end point,  , and another endpoint,  . If both  and  are included in the interval, it is known as a closed interval, and if neither is included it is an open interval. If an endpoint is  , then the interval is unbounded, otherwise, it is bounded.
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More
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Standard Interval Notation
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The standard interval notation is to write the endpoints of the interval separated by a comma, using round brackets to signify that the end point is not included, and square brackets to signify that it is. If an endpoint is  , round brackets are used, since  is not a real number, and cannot be included in an interval.
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Note: Since this is notation, and not an ordered pair, the brackets do not need to match; one endpoint may be included while the other is not, and this is represented by closed and open brackets respectively.
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Graphical Representation
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When representing an interval graphically, a closed or solid point represents that the point is included, while an open point means that it is not.
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Examples
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The closed interval from 3 to 4
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The open interval from -1 to 
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The interval from -4 to -2, including -2, but excluding -4
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Standard Interval Notation
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![[3, 4]](/support/helpjp/helpview.aspx?si=8464/file02283/math196.png)
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Inequality
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Graphical Representation
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