a guess or estimate

Ninety-three million miles is an approximation of the distance of the earth from the sun.

nearness in space, position, degree, or relation; proximity; closeness.

Mathematics, Physics . a result that is not necessarily exact, but is within the limits of accuracy required for a given purpose.

noun

difference , dissimilarity

noun

resemblance , likeness , nearness , similarity , alikeness , conjecture , rough idea , guess , educated guess , ballpark figure , estimation , guesstimate , informed guess , rough measure , circa