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.