mantissa (plural mantissae)
- (obsolete) A minor addition to a text.
- (mathematics) The part of a common logarithm after the decimal point, the fractional part of a logarithm.
- (mathematics, computing, proscribed) The significand; that part of a floating-point number or number in scientific notation that contains its significant digits.
Usage notes 
The use of mantissa to refer to significant digits in a floating point number or scientific notation is discouraged by some in favor of significand, due to earlier distinct usage for the logarithm. It remains in widespread use in the US, however.
Declension of mantissa (type kala)