naturalness

In physics, naturalness is the property that the free parameters or physical constants appearing in a physical theory should take relative values "of order 1". That is, a natural theory would have parameters with values like 2.34 rather than 234000 or 0.000234. This is in contrast to current theory like the standard model, where there are a number of parameters that vary by many orders of magnitude, and require extensive "fine-tuning" of those values in order for the theory to predict a universe like the one we live in.