The

**significand**(also the

*coefficient*or, more informally, the

*mantissa*) is the part of a floating-point number that contains its significant digits. Depending on the interpretation of the exponent, the significand may be considered to be an integer or a fraction.

For example, the number 123.45 can be represented as a decimal floating-point number with integer significand 12345 and exponent −2. Its value is given by the formula:

- 12345 × 10
^{−2}

- 1
**.**2345 × 10^{+2}

*mantissa*, dating at least to the 1940's (see below). This usage of

*mantissa*, while still popular, has been discouraged by the IEEE floating-point standard committee and professionals such as William Kahan. It conflicts with an older usage of

*mantissa*for the fractional part of a logarithm (corresponding to the logarithm of the significand), although this older meaning has grown less common with the disappearance of logarithmic tables in favor of computers.

## Reference

- Arthur W. Burks, Herman H. Goldstine, and John von Neumann,
*Preliminary discussion of the logical design of an electronic computing instrument*, Technical Report, Institute for Advanced Study, Princeton NJ (1946). In J. von Neumann,*Collected Works*vol. 5, A. H. Taub, Ed. (MacMillan, New York, 1963), p. 42.