'on' vs 'upon'

on = upon

They mean the same thing / interchangeable

 

however, 'upon' is more formal than 'on'.

 

He depends on his mother for support at home. 

                        = (same meaning)        

He depend upon his mother for support at home. (more formal)

 

 

Upon

need to use 'upon' sparingly(not much) for literacy effect.

some occasions where only upon will work. 

 - upon is used to emphasize a large number or amount of something. 

ex) mile upon mile of dusty roads 

     thousands upon thousands of letters

     row upon row of seats 

 

common idiots

ex)  once upon a time -

     The summer season was almost upon them again.