Hi, I need help in determining if a system is causal or not. So what I knew is that for a system to be causal is that it has to depend on past and present inputs. However, I don't completely understand the meaning of that definition. So for example if I have a system y(n) = x(n3) how do we know if its input depends on its past inputs or not? i mean obviously if we put in some values of n = 2, it will definitely affect the output of n3=23=8. So the system is then causal? I am really confused about this. Thanks!