Collins COBUILD Advanced Learner's English Dictionary - approximation

(approximations) 1. An approximation is a fact, object, or description which is similar to something else, but which is not exactly the same. That is a fair approximation of the way in which the next boss is being chosen. N-COUNT: oft N of/to n 2. An approximation is a number, calculation, or position that is close to a correct number, time, or position, but is not exact. Clearly that’s an approximation, but my guess is there’ll be a reasonable balance. = estimate N-COUNT