Have there ever been three more similar sounding and confusing words? The first one (perché) will be almost immediately familiar to students of Italian–it is of course the word for both ‘why’ and ‘because’. Confusing enough in itself. Back at school in Florence (goodness knows I’ll be talking about this often enough), I remember being struck by the fact that the teacher would ask a question “Perché…?” and the unfortunate classmate would also answer beginning with “Percheeee…”
However, after a while it becomes familiar enough and it is hard to have a conversation of a decent length without using it at least a few times. The other two words are less intuitive and familiar, and I don’t think I have ever heard them being used in spoken conversation. They are almost exclusively found in written form.
Poiché translates as ‘since’, in the sense of ‘seeing as’ or ‘given that’. For example, ‘Poiché hai guardato il film, puoi dirmi se vale la pena guardarlo’ (since you have watched the film, you can tell me if it’s worth seeing) or ‘Poiché tu non hai l’esperienza, questo lavoro non è adatto per te’ (since you don’t have the experience, this job is not suitable for you).
Now, in everyday speech, you wouldn’t really say it like this. Instead of using poiché, you might rephrase the first sentence as ‘Visto che hai guardato il film,…’, ‘Ho sentito che hai guardato il film. Puoi dirmi…’, or ‘Se hai guardato il film, puoi dirmi…’. The ubiquitous ‘allora’ can also be brought into play here: ‘Allora hai visto il film? Vale la pena…’. In many cases, you would probably use the context of the conversation to leave the ‘since’ portion of the sentence out altogether.
Purché translates as ‘so long as’ or ‘as long as’, and is followed by a subjunctive. For example, ‘Purché lo facciano insieme, sarà tutto bene’ (as long as they do it together, it will be all right), or ‘Purché sia ancora fresca, lo mangio (as long as it’s still fresh, I’ll eat it).
Again, in conversation, purché just sounds far too formal. You might rephrase the first sentence as ‘Sempre che lo facciano insieme,…’ or ‘Speriamo che lo facciano insieme, se no andrà tutto male’, or ‘Se vogliono che tutto vada bene, dovrebbero farlo insieme.’
Although poiché and purché (and similar conjunctions ending with ché) aren’t all that used in spoken Italian, they are widely seen in newspapers and quality literature. For that reason, it’s not a bad idea to become familiar with these slightly confusing yet interesting words.