An
approximation is anything that is similar but not exactly equal to something else. The term can be applied to various properties (e.g., value, quantity, image, description) that are nearly, but not exactly correct; similar, but not exactly the same (e.g., the approximate time was 10 o'clock). Although approximation is most often applied to
numbers, it is also frequently applied to such things as
mathematical functions,
shapes, and
physical laws.