The mantissa of a logarithm is its nonnegative fractional part. If the logarithm
has value 
,
its mantissa is 
,
where 
is the floor
function, and its characteristic is 
. This terminology is used especially for common
logarithms (Stern 2008). For example, a logarithm
with value 
has mantissa 0.14159.
In floating-point arithmetic, mantissa is also used to mean the significand of a floating-point
number (Oracle). This is a different use of the term. For example, the representation
has significand
0.314 and exponent 1. The alternative normalization
has significand
3.14. The significand and exponent
in the former normalization are returned by MantissaExponent[x]
for a positive real number 
.
