What is an approximation of a number based on reasonable assumptions called?

An approximation of a number based on reasonable assumptions is referred to as an estimate. An estimate involves making an educated assumption about a value when precise information is not available, often using known data or logical reasoning to arrive at that approximation. This process is essential in various fields, such as science and mathematics, where exact figures may be difficult or impossible to determine.

Estimates help in making decisions, budgeting, and planning, as they provide a closer representation of reality than a simple guess or a random assumption. Unlike calculations, which require exact measurements or data to produce a definitive result, estimates allow for variability and uncertainty, reflecting the nature of real-world scenarios. Additionally, projections can be similar but are often based on trends and forecasts rather than direct approximations. Thus, the term "estimate" is the most fitting for this context.