logarithm (n.) Look up logarithm at Dictionary.com
class of arithmetical functions used to shorten calculation, 1610s, logarithmus, coined in Modern Latin by Scottish mathematician John Napier (1550-1617), literally "ratio-number," from Greek logos "proportion, ratio, word" (see logos) + arithmos "number" (see arithmetic). Napier invented them and published a table in 1614; the kind chiefly in use were invented by his contemporary Henry Briggs, a professor of geometry at Gresham College, London.