A logarithm is a math tool that tells you what power a certain number must be raised to in order to get another number. For example, the logarithm base 10 of 100 is 2, because 10² = 100.
The word was created by Scottish mathematician John Napier from Greek “logos” (ratio or word) and “arithmos” (number). It roughly means “ratio‑number,” reflecting how logarithms turn multiplication into addition.
Before calculators, logarithms were a revolutionary shortcut that let scientists do huge calculations with pencil and paper. Many things in nature—like earthquake strength and sound volume—are measured on logarithmic scales, where each step up is a giant jump, not a tiny one.
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