@AlanF_US

Alan,

A native speaker from the UK told me once that the difference between "in" and "on" is a matter of context and perspective. Could you, please, try to explain me the difference, no matter how slight it is, between:

I came upon a friend of mine in the bus.

AND

I came upon a friend of mine on the bus.

@Amastan, when I want to understand or explain the difference between phrases in a language, I generally do a search query on the Internet using "or" or "vs" or "versus". In this case, a search for

"in the bus" vs "on the bus"

brings up a number of pages that explain the issues more fully than I can. Here's one from the English Language Learners Stack Exchange forum, which is generally a good place to go:

https://ell.stackexchange.com/q...-or-on-the-bus

Basically, you can practically always use "on the bus". Contexts where "in the bus" would be correct are considerably less common.

Alan,

"Basically, you can practically always use "on the bus". Contexts where "in the bus" would be correct are considerably less common."

This is the type of answer I was looking for :-) I'm at a stage of "learning" where I prefer to hear/read simpler answers from native speakers instead of (re-)studying those subtle differences the way a teacher or a linguist would do it. A few years ago, I used to talk to an English native speaker from the UK and he would answer me the way he would answer his friend or brother with replies like "I think that this form is more formal than that one" or "I think that this form is more common than that one" or "I think that this is rather Scottish and North American." At the beginning, I was kind of "frustrated" by his "I think" replies, but I quickly liked that because what his "wild guesses" to my rather difficult questions could be verified by me by paying more attention to the way native speakers used this or that word or expression I asked my friend about.

Long story short: I liked your last two lines :-)

Thank you very much, Alan!

You're welcome.