They are mostly interchangeable. There are nuances though, so even the tone of voice is important.
If you are using a serious / formal tone of voice, and you are in a debate / polemic context, you may prefer "Per piacere" to underline that what you're asking is due.
If, given the context, you are at a disadvantage, you could use a smoother tone along with "per favore" to highlight that you're asking some sort of preferential treatment, although not due. You're not begging, just flattering a little.
That said, one could demand you something using "per favore", or ask you a favour using "per piacere". Don't take them as rules; they're just, as I said, nuances.
It's a polite imperative: http://italian.about.com/library/weekly/aa011900a.htm
Because "would" "could" or "should" is using conditional, which like in English is used to be polite. ('potresti passarmi il burro?" ) But this is imperative, which is a simple instruction to pass the butter. This unit is on subjunctive so this exercise isn't meant to be here. It's only words in subjunctive and polite imperative are the same. But they're different grammatical concepts :)
The author of the cited article doesn't seem to understand English imperative. She says:
"Be good! Stay home! Let's go!
"When we say the above phrases in English, the only hint that it’s a command or a suggestion is our tone. Unlike Italian, we don’t have a special way of changing the verb that makes the situation obvious."
Does any English-speaker have any trouble determining that "Be good" is a command? I certainly don't, and I don't need tone of voice to tell what it is: an Imperative mood command to be good.
Yes, on my first trips to italy inter-railing I was forever saying "mi scusi" as I weaved up train corridors threatening to squash italians with my rucksack. I must have learned it as a set phrase. Only recently have I realised that it was the subjunctive. Enlightenment comes to all eventually :)
Unfortunately wrong kind of light :-) "Mi scusi" is imperative mood and not subjunctive mood. But, you are not that wrong, and here is a short explaination:
We have to go back to the roots, the latin, and the imperative mood. It happens to be so that they simply didn't have imperative in the third person. When the Italians formed their grammar, this was quite unacceptable, you have to be able to be imperative in a polite mood too! So what did they do? You guessed it, for the third person polite mood Lei, you conjugate the verb as you do in subjunctive.
ah, interesting. So you are saying that it is an imperative but written the same way as the subjunctive? I was aware that I was being polite as in, would you .... Looking forward to your reply. My other favoured phrase by the way on my early Italy travels was "Non lo so, sono inglese". I found that accounted for/excused almost any stupidity.
True, they took the subjunctive pattern since there was no imperative to take. And frankly I think it makes some kind of reason.
To start with, the Latin Romans, didn't "Lei" each other, so for them, this was of course no problem. What would happen if with rephrase and throw in some polite, humble, doubts in this? Subjunctive of course:
Spero che ti mi scusi. Spero che Lei mi scusi. (No eqv in latin)
Compare with imperative:
Scusami! (True imperative, subject hook on to the end of the verb) Mi scusi! (The "invented" imperative, with subjunctive pattern, no eqv in latin)
The interested may check out how it is solved in the other latin languages :)
Right. In Italian, you call this way to address somebody "dare del Lei". (EDIT: where "Lei" is literally "She", but in this case translates with "you" formal).
What they won't tell you, is that using the 3rd person does not suffice: you have to use subjunctive (instead of simple present).
This kind of polite addressing is similar to "Sie..." usage in German.
It might be helpful to other readers of this exchange to read about the origins of the use of the third-person singular feminine pronoun as a polite form of address. Here are a couple of links that explain it (one in Italian and the other in English):
Here's another link to a scholarly treatment of the subject with regard to German ("The German Address System: Binary and Scalar at Once"):
According to the latter article, the use of the third-person singular feminine pronoun as a polite form of address in German is attested by the end of the 16th century and later was used with plural verb forms.
"Lei" (upper case) in this form is "you". "lei" (lower case) is "she". It is the polite, or formal, "you", but it is still second person singular. Just as the formal second person plural is "Loro" (upper case). The confusion arises because they are similar to third person pronouns and take third person verb forms in all tenses. For commands, that tense must be the subjunctive (congiuntivo).
You are correct in that it is similar to the formal "Sie" (upper case) in German (note the parallel that "sie" (lower case) also means "she"). The only difference here is that "Sie" is both singular and plural. Also, the formal German commands take the infinitive, not the subjunctive.
The imperative (l'imperativo) is used to give orders, advice, and exhortations.
Examples: Spiegaci!, = Explain to us!, Girati! = Turn around!, Non tormentarmi = Don't torment me!, Sbrigati = Hurry up!, Chiamami! = Call me!, Scrivimi! = Write me!, Sta' zitto! = Shut up!, Lasciami in pace. = Leave me alone., Mettila dietro. (una bici) = Put it in the back. (a bike), Non dirmelo! = Don't tell me!, Non fare l'innocente. = Don't play innocent., Divertiti! = Enjoy yourself!, Dille di riprendersi. = Tell her to get better., Non preoccuparti. = Don't worry yourself., Calmati! = Calm down!, Digli di chiamarla. = Tell him to call her., Tocca a te! Your turn!, Si accomodi. = Make yourself comfortable., Trascinalo a scuola! = Drag him to school!, Coprimi! = Cover me!, Vattene! = Get out of here!
imperativo presente [passàre] = present imperative [to pass]
pàssa [non passàre] (tu) .......... pass [donʻt pass] (informal, singular)
pàssi (egli) .......... pass (formal, singular)
passiàmo (noi) .......... letʻs pass
passàte (voi) .......... pass (informal, plural)
pàssino (essi) .......... pass (formal, plural)
I don't think it's polite imperative (Lei-form). If it were, then Italians would say «Mi faccia il caffè, per favore» but they don't. They always say «mi fai un caffè, per favore». So I guessed that it's just the 2nd person indicative form used somehow to express the request or command. Am I wrong?
Yes, I think so. The verb is passare as you know so the 2nd person indicative would be 'passi' as you state. But it's not the familiar imperative, that'd be 'passa'. 'Passi' is the formal or polite imperative formed by the present subjunctive, not the present indicative. I'm not a native, but I believe that's correct. You can see it perhaps more clearly if you look at the verb 'dire'. 2nd person indicative is 'dici' and the formal or polite imperative is 'dica' as in 'mi dica'; well if you check you'll see that 'dica' is the present subjunctive.
Since Italian technically has no verb forms in the imperative mood for the 3rd person, when you're using the polite (3rd-person singular) form of address with someone and want to express an imperative idea, you would ordinarily use the subjunctive. "Passi" here is the 3rd-person singular subjunctive of "passare." You will hear this form used frequently in polite conversation ("venga," "si accomodi," ...).
Can someone confirm whether this is asking someone formally (Lei) to pass the butter? Since passare is an -are verb, if it were asking "tu" to pass the butter, it would be "Mi passa", so I can only assume that this is asking "Lei (formal you)" since the ending is "-i". Just looking for confirmation that I'm thinking about this correctly.