what do you mean when you say "by chance" - like in "i met her by chance" (or "i happened to meet her") ?

i explain.... this is one of the cryptic exercises a teacher gives us. He asked to explain what we think without drowning in books - so i thought it would be nice to report some ideas from different people ( and if possible from people speaking different languages, so if your mothertongue is not english, your help will be very welcome)

thanks (and spaghetti) to all.