A ' is any set consisting of a single real number (i.e., an interval of the form ). Some authors include the empty set in this definition. A real interval that is neither empty nor degenerate is said to be proper, and has infinitely many elements.
A ' is .any set consisting of a single real number (i.e, an interval of the form ). Some authors include the empty set in this definition A real i.nterval that is neither empty nor degenerate is said to be proper, and has infinitely many elements.