[FlorenceArt]

In French we have a simple rule: any word imported from a foreign language becomes a French word, and follows French rules for forming a plural (just add an s at the end). Therefore, the plural of scénario is scénarios. Simple. Though of course there are always people trying to look clever by using scenarii. Also note the accent, which I don't suppose exists in the original language (Italian I assume).

Seems much simpler and practical to me. How are we supposed to know and apply the grammatical rules of all the languages we borrow from? And, as Harry's example shows, how are we even supposed to know which language we're borrowing from?

Most words change meaning when they hop from one language to another, why should we insist that they are still foreign words? They are not, they are French (in my case), or English, words with a foreign origin.