Significand - Use of "mantissa"

Use of "mantissa"

In American English, the original word for this seems to have been mantissa (Burks et al.), and as of 2005 this usage remains common in computing and among computer scientists. However, this use of mantissa is discouraged by the IEEE floating-point standard committee and by some professionals such as William Kahan and Donald Knuth, because it conflicts with the pre-existing use of mantissa for the fractional part of a logarithm (see also common logarithm).

The confusion is because scientific notation and floating point are log-linear representations, not logarithmic. To multiply two numbers, given their logarithms, one just adds them – adds the characteristic (integer part) and adds the mantissa (fractional part). By contrast, to multiply two floating point numbers, one adds the exponent (which is logarithmic) and multiplies the significand (which is linear). Using "mantissa" for both terms obscures this distinction and creates a risk of confusion.