>>10976613There are different definitions of it that are all equivalent in practice. Someone already replied to you with the thermodynamic definition. I almost prefer that one, because it reminds people this is an idea from physics and not some armchair philosophizing bullshit.
But if you want what is known as the 'microcanonical' definition, the idea is that in anything we see macroscopically we don't know the detailed microscopic positions and velocities of all the molecules. Some macroscopic states, which are defined by things we can measure like pressure and temperature, will be compatible with more microscopic states, which are defined by the exact position and velocity of molecules.
If is the number of microscopic states compatible with a macroscopic state, the entropy S is just
k is just an unimportant constant to make the units agree with the thermodynamic definition the other anon gave. If we use better units for temperature it goes away
