(i) Do not confuse depend on/upon and the more formal phase, be dependent on/upon. Compare: Depends on/upon: ‘The speed of a car depends on the size of the engine.’ Be dependent on/upon: ‘The speed of a car is dependent on the size of the engine.’(ii) Depends on/upon means ‘be shaped or determined by’(it is not used in progressive tenses): ‘His success depends on/upon his effort.’  (iii) ‘It depends on whether (NOT if): ‘We don’t know yet. It all depends on whether the car is fixed in time.’
