While referring to these prepositions, I want to emphasize their differences about their manner and common expressions. I do not understand, for instance, why the preposition ”on” it is used to say ”how did you do on the test?”, and, by contrast, you use ”in” to say ”in this chapter, we will talk about...”

I do not understand that. Moreover, I don't understand how to notice the difference between those prepositions. Is there any particular form to choose between them?

  • We have lots of questions about prepositions - they’re very confusing in English, and often you just have to memorize which one is correct with which word. Here is a search that will list some of the questions we have dealing with “in” and “on”: ell.stackexchange.com/… in case you would like to read more about the differences and see what other learners have asked about.
    – ColleenV
    Jun 10, 2019 at 19:35

1 Answer 1


If you are speaking literally, "in" usually carries the meaning of "surrounded by", or "completely enclosed":

"There's a fly in my soup."

"The dog is in the doghouse."

"I made an error in that sentence."

and "on" implies "attached to" or "touching":

"I wish I were a fly on the wall."

"They were on bikes."

"We put another coat of paint on it."

But it's a little bit trickier when you are speaking figuratively, using idiomatic expressions, or discussing abstract ideas where the physical concept of "completely surrounded" vs. "merely touching on the outside" doesn't really apply.

When it comes to set expressions like "on the bus", "in synch","on the team", or the cases you mention, "on the test" or "in this chapter", often these just have to be learned by rote.

Not to mention confusing pairs like:

"on fire" vs. "in flames"


"on the money" vs. "in the money"

Many of these are not subject to reason at all, just custom.

Sometimes it will even vary by region. Where I come from, people "stand in line", but my husband always refers to people "standing on line". He claims that's the way they say it in New York City.

Another example is the comment of Ronald Sole above, where he says, "In the test is more common than on the test." But in the variety of English spoken where I live, (California, USA), it is just the opposite. We would be much more likely to ask, "How did you do on the test?" than "in the test."

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