Estimation is the approximation of a result that one can use with information that is not clear or is incomplete. It is like making an educated, reasonable guess based on the information given.

If an estimate is more than the actual amount, then it is called an overestimate.^[1] If the estimate was less than the actual result, then it is called an underestimate.^[2] This is different from a prediction.

• Estimation chapter from "Applied Software Project Management" (PDF)