[Mathematics] a fractional number n/d, where n and d are integers, n is the numerator and d is the denominator. The set of all rational numbers is usually called Q. Computers do not usually deal with rational numbers but instead convert them to real numbers which are represented (approximately in some cases) as floating-point numbers. Compare irrational.
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Nearby terms: Rate monotonic scheduling « RATFIV « RATFOR « rational » RATional Fortran » Rationalized C » rave