A number representation consisting of a mantissa, M, an exponent, E, and an (assumed) radix (or "base") . The number represented is M*R^E where R is the radix - usually ten but sometimes 2.
Many different representations are used for the mantissa and exponent themselves. The ieee specify a standard representation which is used by many hardware floating-point systems.
See also floating-point accelerator, floating-point unit.
normalisation is the process of converting a floating point number into canonical form where any number other than zero has a mantissa whose first digit is non-zero.