- a quantity representing the power to which a fixed number (the base) must be raised to produce a given number.
Logarithms can be used to simplify calculations because the addition and subtraction of logarithms is equivalent to multiplication and division, although the use of printed tables of logarithms for this has declined with the spread of electronic calculators. They also allow a geometric relationship to be represented conveniently by a straight line. The base of a common logarithm is 10, and that of a natural logarithm is the number e (2.71828...)
early 17th century: from modern Latin logarithmus, from Greek logos 'reckoning, ratio' + arithmos 'number'