borderline case in the logical sense, a case that falls within the ‘gray area’ or ‘twilight zone’ associated with a vague concept; in the pragmatic sense, a doubtful, disputed, or arguable case. These two senses are not mutually exclusive, of course. A moment of time near sunrise or sunset may be a borderline case of daytime or nighttime in the logical sense, but not in the pragmatic sense. A sufficiently freshly fertilized ovum may be a borderline case of a person in both senses. Fermat’s hypothesis, or any of a large number of other disputed mathematical propositions, may be a borderline case in the pragmatic sense but not in the logical sense. A borderline case per se in either sense need not be a limiting case or a degenerate case. See also DEGENERATE CASE, LIMITING CASE , VAGUENES. J.Cor.