Charge question made me shut !!! My younger sister just started learning about electrons and charge associated with it, while she was studying , she asked me "what is a charge " and this question made me shut !! i wasn't able to answer (we might say that its a property but that's not a good answer at all) . So do we have any definition of charge, like for mass, we can say its just same as energy stored in a different form (E=mc^2). do we have any such relation of charge with energy or something..... if we have then that relation can be used to combine gravitation and electrodynamics, and hence GUT can be developed ????