logarithm (lŏgˈərĭħəm) [key] [Gr., = relation number], number associated with a positive number, being the power to which a third number, called the base, must be raised in order to obtain the given positive number. For example, the logarithm of 100 to the base 10 is 2, written log10 100 = 2, since 102 = 100. Logarithms of positive numbers using the number 10 as the base are called common logarithms; those using the number
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