On Vs Upon: What’s the Difference?

Knowing when to use on vs upon is a tough grammatical question, but I’ll straighten you out here.

Remember seventh grade, when your teacher stood at the front of the room and wrote various prepositions on the blackboard or whiteboard, expounding the difference between on vs upon? Perhaps they illustrated the point with a cat playing around a table, or a hiker exploring a mountain.

If that didn’t stick with you, you’re not alone. Prepositions are one of the most difficult parts of speech to use properly, but if you can master them, your writing will shine. 

The good news is, you don’t have to wonder about on and upon any longer – here’s the lowdown on these useful words, so you’ll never make a misstep again.

On and Upon: Essentially the Same Meaning

Let’s start with the straight answer. On and upon are synonyms and they basically mean the same thing: something is in contact with another object and is supported by it. It is not enough to have the first aspect, because other preposition words indicate two objects in contact with one another, such as:

• Against
• Among
• Into
• Onto
• Within
• Through

Similarly, there are many prepositions that can mean something is higher than something else in physical space, like upon and on, but that don’t necessarily imply contact. Directly, those include “over” and “above.” Indirectly, prepositions include:

• Near
• Outside
• Without
• Beyond

Note that not all prepositions are one word, either. “On top of” is a prepositional phrase that means the same thing as “on” and “upon.” It is only the latter two that are single words, implying both contact and a higher position in space.

That said, if there is a difference between those two words, what is it?

A Matter of Semantics

While you now know that the two words mean basically the same thing, it’s important to point out that one is more often used in the abstract sense. There are only subtle differences between “on” and “upon,” but used in more formal writing, there is a preferred choice: upon.

There is no hard and fast rule about this, mind you. Simply put, some people think using the longer word approves readability in American, Australian and British English. As “on” is a considerably more common word in English, moreover, using “upon” where it fits can help reduce word echoes (the repeated overuse of one word or phrase) in your writing.

Typically, though, you should save “upon” for your essays and high-end work emails, and ditch it in everyday language, fiction dialogue and more intimate emails.

In a few very special cases, only one word works. Think “once upon a time” or “on the lam.” These are phrases native language speakers intuitively know and would never substitute in the wrong preposition.

English language learners would only encounter these phrases in their entirety, so it’s not something you need to worry about no matter who you are.

Where Does “Based” Fit In?

Many people use the word “based” in conjunction with a preposition to indicate that something follows from something else, typically a thought, principle or work of art. The idea is that the original idea or work provides a foundation or “base” for whatever follows.

For instance, a movie is “based off of” a book, or a meeting date gets determined “based on” everyone’s schedule. There are a lot of different ways to use this prepositional phrase, actually. These include:

• Based on
• Based upon
• Based off
• Based off of

That’s … a lot of possible choices for the same darn meaning. Which is correct, you’re wondering, and who the heck invented a language that would put a poor grammar student through so much agony??

Deep breaths. It might surprise you to know that, according to Merriam-Webster, you can use all of the above freely. The first two are older constructions, and thus they are more widely recognized in English. The use of “based upon” is again more likely to show up in formal writing than in everyday vernacular.

The newer two, using the word “off,” are also acceptable. However, some people are inclined to think they are wrong just because they are less well established. You can rest comfortably knowing that’s not true – and feel free to correct your superiors at cocktail parties.

(Actually, maybe don’t do that.)

Other Common Uses of “On” and “Upon”

These prepositions show up in many other phrases as well. Common ones you’ve likely heard include:

• Touched on/upon: covered in a brief way during a conversation or written communication
• On/upon arrival: something will happen when someone/something gets somewhere
• Contingent on/upon: something will only happen if something else does
• Incumbent on/upon: someone is responsible for ensuring that something happens
• Reflect on/upon: thinking about an idea, event, or proposal in depth

There are other examples, of course, but the main takeaway here is that you can freely use “on” or “upon” for any of these constructions. The same goes for any other phrase that uses either.

The Final Word: On Vs Upon

Hands down, this is one of the easiest grammatical questions for native language speakers and English language learners alike. The answer is simply that “on” and “upon” are completely interchangeable.

Remember that if you’re trying to sound more formal, “upon” might prove the better choice. Ditto if you’re talking about an academic idea or principle. On the other hand, “on” is often the more reached-for option for informal communications and everyday speak.

Nevertheless, both are correct ways to indicate that something is on top of and touching something else. More metaphorically, they mean that something is closely related to something else. Unless it is a specific idiomatic phrase (“once upon a time”), you can use both freely for either meaning! If you liked this post, you might be interested in our as vs. like explainer.

FAQs About On Vs Upon