An example of mantissa is 234 in the number 1101.234.
Origin of mantissaL, (useless) addition, makeweight, gain, uncertain or unknown; perhaps via Etruscan from Celt: uncertain or unknown; perhaps so named because it supplements the integral
Origin of mantissaLatin makeweight perhaps of Etruscan origin
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.
From Latin mantissa, mantÄ«sa, of unknown origin (said by Festus to be a loanword from Etruscan, but it may actually be from Celtic, possibly through Etruscan mediation).