On or Upon

On or Upon

By Alena Lien, 

19 April 2021

I explain the differences between the prepositions, "on" and "upon."

Because "on" has so many definitions, I will first explain the differences by focusing on "upon" and then provide situations where "on" and "upon" can be interchangeable.



1.   "Upon" is very formal compared to "on."

Although interchangeable, "upon" is often too formal for conversational English - "on" is more common and acceptable.

Use "on" most of the time, and use "upon" sparingly.

Compare the following:

  • "I left the books on the table."

  • "I left the books upon the table."

Although both sentences are the same, using "upon" sounds quite old-fashioned and less natural.

-   In very formal and legal language.

  • "The title was bestowed upon him by the Queen in 1998."

  • "The proceedings were served upon the defendant last week."

-   Literary use or period literature, movies and tv shows.

  • "I sincerely believe we were put upon this planet for this very purpose."

  • "He put his bowler hat upon his shiny, bald head and briskly walked away without so much as a farewell."

2.   There are some common idiomatic expressions with "upon."

Using "on" is possible, but less common.

-   "Once upon a time" (expression) - used at the beginning of children's stories to mean "a long time ago."

This cannot be used with "on."

  • Once upon a time, there lived a beautiful maiden.

Not - Once on a time, there lived a beautiful maiden. 

-   "Chance upon/on (someone/something)" (idiom) - to find something or meet someone by accident.

"On" can be used, but this is less common.

  • "We chanced upon a fossil while taking a stroll on the beach."

  • "I chanced upon an old friend at the supermarket yesterday. We hadn't seen other in years."

-   "Take (something) upon/on (onself)" (idiom) - to accept responsibility for doing something without being asked.

"On" can be used, but this is less common.

  • "Thanks for taking it upon yourself to organise the event."

  • "She's taken it upon herself to care for him but I'm not sure if that's such a good thing."

- Be upon (somebody) (formal expression) - something will happen very soon.

"On" cannot be used.

  • "It won't be long before winter is upon us again."

Not - "It won't be long before winter is on us again."

-   "Be put upon" (informal phrasal verb) - to be treated badly by someone who takes advantage of your desire to be helpful.

To me, this is not very common.

  • "I don't mind but I can't help being put upon."

Not - "I don't mind but I can't help being put on."

"Put on"

"Put on" has a number of different meanings but requires difference sentence structures, which is why the previous example does not work. 

-   "Put on someone" (informal phrasal verb) - to tease or playfully deceive someone.

  • "I don't mind but I can't help like he's putting me on."

-   "Put-on" (informal noun) - an attempt to deceive someone into believing something that is not true.

  • "I don't mind but I can't help feeling like it's a put-on."

3. "Upon" can mean "immediate/soon after."

This is sometimes interchangeable with "on."

  • "Visitors will be tested upon arrival."

  • "Visitors will be tested on arrival."

  • "Upon his return, he realised he lost his wallet."

  • "On his return, he realised he lost his wallet."

+ Gerund phrase - using "on" can sometimes sound weird.

  • "We congratulated Wally upon hearing the good news."

  • "We congratulated Wally on hearing the good news."

These sound okay to me.

"Wally's son moved out upon leaving school."

Not - "Wally's son moved out on leaving school."

"Upon watching the documentary, we decided to change our diets."

Not - "On watching the documentary, we decided to change our diets."


- "On" can be used to show when something happens, so this refers to a specific time.

  • "We visited my grandmother on Friday."

Not - "We visited my grandmother upon Friday."

4. "Upon" can be used to emphasise a large number or amount of something.

"Upon" is placed between two of the same nouns. This can sound more literary and poetic.

  • "All I saw were thousands upon thousands of bright pink flowers."

Not - "All I saw were thousands on thousands of bright pink flowers."

  • "He waited for her year upon year, but never heard from her."

Not - "He waited for her year on year, but never heard from her."

Please note: "year-on-year" is a finance term to compare the financial results in the previous year.

When "on" and "upon" are interchangeable

There are situations where "on" and "upon" are interchangeable. Bear in mind however, that "on" is usually preferred and "upon" is more formal.

-   On/onto an object or surface.

  • "The cat is relaxing on/upon the shelf."

  • "I left the books on/upon the table."

-   Supported by a part of your body.

  • "Do cats always land on/upon their feet?"

  • "He dropped down on/upon his knees."

-   Looking at something.

  • "Her eyes fell on/upon the photograph of her grandmother."

-   Towards someone or something.

  • "The attacks on/upon their homes left them devastated."

-   Indicate someone or something is necessary.

  • "I had to rely on/upon my parents for a while before I found a job."

  • "Although work experience is important, some emphasis should be placed on/upon the candidate's level of education.