Help: my car can not start

My car is toyota 03, I drove yesterday, it happen when I turn the key the car's not start at beganning then I try second time and stay the start position longer time, the car start, I am not pay attention I thought is ocasional happen.  But today the car is totallly died other involved the power like light window is fine only can not start the car, I need the car go to work tomorrow,  It is because the battery ? it is 4 yeras old. Thanks for your help.