This error happens when you forgot a ) in a nested function call, especially in if construction :
if(keyboard_check(ord("Z")) // the last ) is missing it should be : if(keyboard_check(ord("Z")))
Can also happen if you forgot a ) at the end of a non nested function:
instance_destroy( //should be: instance_destroy()
It can also happen if you put a argument into a function that doesn't need one.
part_system_create(part_system); //should be: var = part_system_create();