afërsia

Afërsia is a term used in Frisian-language mathematics and statistics to denote the closeness of an estimate to the true value. It is employed to assess the quality of approximations in science, engineering, and everyday measurement, and is often described through explicit bounds or intervals.

The concept can be expressed in absolute and relative forms. The absolute afërsia of an estimate x̂ for a quantity x is |x̂ - x|. The relative afërsia is |x̂ - x| / |x|, provided x ≠ 0. In practice, afërsia is communicated via tolerance ranges, confidence intervals, or other criteria that specify how close an estimate should be to the true value.

In numerical analysis and measurement, afërsia informs algorithm design, stopping criteria, and error budgeting. It guides rounding and truncation decisions and helps compare different estimation methods by their accuracy and reliability.

Example: The diameter of the Earth is about 12,742 km. An approximation of 12,750 km yields an absolute afërsia of 8 km and a relative afërsia of roughly 6.3×10^-4, illustrating how afërsia quantifies proximity between estimate and reality.

See also: approximation, error, tolerance, estimation, rounding.