Mantissa

In scientific notation the mantissa is the digits without the ×10ⁿ part.

Example: in 5.3266 × 10³ the mantissa is 5.3266

Also known as the significand.

(Note: in some rare cases the mantissa can also mean the part of a number after the ".", so in 2.71828 the mantissa would be 0.71828)