These phrasal verbs have a similar meaning (please correct me if not):
- run into
- come across
- come upon
Are there any nuances to choose between them? For example, I might be wrong but I mostly see run into used for meeting a person unexpectedly.
My understanding of responses so far:
- come upon is not very common any more
- run into is the most frequently used one
- run into might or might not have a negative connotation (No consensus as I see it)
Perhaps working on some concrete sentences might give a better result. For example, which one would you use for (in parentheses are my first thoughts):
- Unexpectedly meeting a dangerously fierce pack of dogs on the street (run into)
- Unexpectedly meeting a very beautiful girl whom you don't know on the street (come across)
- Unexpectedly finding a book that you had lost (come across)
- Unexpectedly finding a grammar mistake in a blog that you'd love to point out (come across)
Maybe I should've mentioned stumble upon too.
By the way, sorry about the length of the post. I had to expand it to clarify the context.