Crossword clue: the decimal part of a logarithm, as distinguished from the integral part, or characteristic.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
the positive fractional part of the representation of a logarithm; in the expression log 643 = 2.808 the mantissa is .80