Definition of mantissa in US English:



  • 1Mathematics
    The part of a logarithm that follows the decimal point.

    • ‘The mantissa provides the significant information, or digits, and the exponent provides a scaling factor that shows how big the number is.’
    • ‘Sharp and completely accurate visions of hexadecimal mantissas and binary fractions floated about my head, along with the sure and certain knowledge of how to convert them to something more useful.’
    • ‘By choosing appropriate mantissas and exponents, we can increase the resolution at shallower depths and degrade it at greater depths.’
  • 2Computing
    The part of a floating-point number that represents the significant digits of that number, and that is multiplied by the base raised to the exponent to give the actual value of the number.

    • ‘Double-precision fixed-point would employ two times 24, or a 48-bit word length; double-precision floating-point would use a two times 32, or 64-bit mantissa.’
    • ‘In these cases, the 24-bit fixed standard is equivalent to the 24-bit mantissa, plus 8-bit exponent used in the 32-bit, floating-point version.’
    • ‘If you recall, run-of-the-mill DSPs typically store numbers as a floating-point, 24-bit mantissa and an 8-bit exponent.’


Mid 17th century: from Latin, literally ‘makeweight’, perhaps from Etruscan.