Science is defined as a body of information obtained by methods based on observation. Physics, chemistry and other lab sciences enjoy the ability to repeat experiments in order to test whether results are reproducible.
Historical sciences don’t enjoy the repeatability. Examples are geology, evolution, etc. These sciences depend on observation but are not able to go back in time to repeat the experiment
Then, there are the really fuzzy sciences such as sociology and psychology. They are fuzzy because of the wide variation in the objects that are being observed.
If it ain’t falsifiable, it’s opinion.