Definitions
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. that part of a floatingpoint number that contains its significant digits.
Etymologies
Sorry, no etymologies found.
Examples

If all of the first 40 bits of the double's significand are set, bits 1 to 39 are cleared and the exponent is incremented.

Inf, the real's exponent and significand fields are filled so as to represent the largest value possible, the sign bit is transferred, and the code prInf is returned.
ruzuzu commented on the word significand
"In American English, the original word for this seems to have been mantissa (Burks et al.), and this usage remains common in computing and among computer scientists. However, the term significand was introduced by George Forsythe and Cleve Moler in 1967, and the use of mantissa for this purpose is discouraged by the IEEE floatingpoint standard committee and by some professionals such as William Kahan and Donald Knuth, because it conflicts with the preexisting use of mantissa for the fractional part of a logarithm (see also common logarithm). For instance, Knuth adopts the third representation 0.12345 × 10+3 in the example above and calls 0.12345 the fraction part of the number; he adds: "it is an abuse of terminology to call the fraction part a mantissa, since this concept has quite a different meaning in connection with logarithms".
The confusion is because scientific notation and floatingpoint representation are loglinear, not logarithmic. To multiply two numbers, given their logarithms, one just adds the characteristic (integer part) and the mantissa (fractional part). By contrast, to multiply two floatingpoint numbers, one adds the exponent (which is logarithmic) and multiplies the significand (which is linear)."
 https://en.wikipedia.org/w/index.php?title=Significand&oldid=850602451 (citations and emphasis removed)
August 8, 2018