katrielalex wrote::D
OK, so it's not correct. I admit defeat.
You must all now say "octopodes" instead of "octopi".
Kati
P.S. Octopus is originally a Greek word so the Latin plural 'octopi' can't be right. It's either octopuses or octopodes.
Kati, English is a language of exceptions. In some cases English will apply the rules of the root language and in others it won't. Accepted usage comes from common parlance not the application of rules. This seems reasonable, since the role of language is allow someone to make themselves understood to others. This makes for a very rich, diverse vocabulary, if not sometimes a little confusing for non-native speakers. You should note that this fact is accepted even by the mighty OED whose role is not to define the English language, but to document it as it changes (rapidly) over time.
Use fori if you wish, but most people won't understand what you mean.