Common logarithms are logarithms with a base of 10. They are often written as log(x) or log₁₀(x), where x is the number you want to find the logarithm of. The common logarithm answers the question: "To what power must 10 be raised to obtain x?" For example, log(100) equals 2 because 10² = 100. Common logarithms are widely used in various fields, including science, engineering, and finance. They simplify calculations involving exponential growth or decay, making it easier to work with large or small numbers. Common logarithms are also essential in calculating pH in chemistry and in decibel levels in acoustics.