Word Choice – On or Upon

Sandra’s question: “Is it correct to say the dog jumped ‘up on’ the roof or the dog jumped ‘upon’ the roof? I see a lot of these mixes nowadays.”

BizWritingTip response:  Yes, both sentences are correct. However, they express slightly different ideas. Up on means to move in an upward motion onto a surface. Upon just means on a surface.  In fact, the prepositions — on and upon — are often interchangeable although on is usually preferred. Upon is considered more formal.

Examples (correct)
The dog jumped up on the roof. (The dog moved itself upward onto the roof.)
The dog jumped upon the roof. (This is formal way of stating that the dog moved onto the roof.)
The dog jumped on the roof. (This is considered a less formal way of saying the dog moved onto the roof.)

On and upon are also used with the verb based.

The book is based on the life of Lady Duff Gordon.
The book is based upon the life of Lady Duff Gordon. (This is a more formal statement.)

There are, however, a few expressions that require you to only use upon.

Once upon a time
Row upon row of seats
Summer is almost upon us.