The docstring for various sizes arguments states that size is given as symbol area in square points. Checking with matplotlib.Collections code, this argument doesn't actually calculate the symbol area, but instead is a squared scale factor. This might lead to a wrong interpretation especially if irregularly-shaped symbols are used, but it also not correct for circles. On a more general basis, is it not easier to use linear scale factor as an argument, instead of its square? I just don't see applications where the latter is more useful than the former.