"Approximation" refers to a guess or an estimate that is close to the actual value or truth, but not exactly precise. It is a way to give a rough idea or approximation of something without having all the exact details. Full definition
Floating point number systems are a method of representing approximations of real numbers (they can be helpful for computing because it is impossible to store numbers with infinite precision). (eff.org)
These previews are a very good approximation of what the final item will look like but they are not exact. (looplooks.net)
The links go to the download sites, so that should be a close approximation of how many books are actually given away. (janefriedman.com)