Per colpa della pioggia, restiamo in casa.

Per colpa di means because of or due to, but with a clearly negative feeling. It suggests that something is happening through the fault of something unpleasant.

So in this sentence, Per colpa della pioggia means Because of the rain or more literally It’s the rain’s fault.

If you want a more neutral expression, Italian often uses a causa di: A causa della pioggia, restiamo in casa.

Because di + la contracts in Italian.

• di + la = della

So:

• colpa di la pioggia → incorrect
• colpa della pioggia → correct

This kind of contraction is very common in Italian:

• di + il = del
• di + lo = dello
• di + la = della
• di + i = dei
• di + gli = degli
• di + le = delle

In Italian, nouns often keep the definite article in places where English would not use one.

English says: because of rain

Italian normally says: a causa della pioggia per colpa della pioggia

So the article is part of the natural Italian structure. You usually would not say per colpa di pioggia in this sentence.

Restiamo is the present indicative, first person plural form of restare.

So:

• resto = I stay
• resti = you stay
• resta = he/she stays
• restiamo = we stay
• restate = you all stay
• restano = they stay

Here, restiamo means we stay or we are staying.

Italian often leaves out the subject pronoun, so noi restiamo is possible, but restiamo by itself is completely normal because the verb ending already shows we.

Yes. Restare and rimanere are often interchangeable and both can mean to stay or to remain.

So this would also be natural:

Per colpa della pioggia, rimaniamo in casa.

In many everyday contexts, the difference is small. A learner can usually treat them as near-synonyms here.

Both can work, but they are not exactly identical.

• in casa = inside the house, indoors
• a casa = at home

In this sentence, in casa highlights the idea of staying indoors because of the rain.

So:

• Restiamo in casa = We stay indoors / inside the house
• Restiamo a casa = We stay home / remain at home

Both are possible, but in casa fits especially well when the contrast is with going outside.

Because Italian usually drops subject pronouns when they are not needed.

The ending -iamo already tells you the subject is we, so restiamo is enough.

• Noi restiamo in casa = correct, but more explicit or emphatic
• Restiamo in casa = correct and more natural in many cases

This is very different from English, where you normally must say we stay.

The comma is natural because Per colpa della pioggia is an introductory phrase.

So this is good: Per colpa della pioggia, restiamo in casa.

You can also put the cause at the end: Restiamo in casa per colpa della pioggia.

Both are correct. The difference is mainly emphasis:

• Per colpa della pioggia, restiamo in casa. → highlights the cause first
• Restiamo in casa per colpa della pioggia. → states the action first

Sometimes, but restiamo is better here.

Restare suggests staying somewhere, especially instead of leaving or going out. That fits the idea of rain preventing you from going out.

Stare can sometimes describe being somewhere, but in this sentence it is less precise.

So:

• restiamo in casa = we stay indoors
• stiamo in casa = we are in the house / we stay in the house, but it is less specifically about remaining there because of a reason

If you are learning, restiamo in casa is the safer and more natural choice in this context.

Usually, yes. It normally introduces a cause the speaker sees as bad, annoying, or undesirable.

That is why it works well with rain in this sentence: the rain is stopping the speakers from doing what they might otherwise do.

A useful comparison is:

• per colpa di = because of, in a blame-like or negative way
• a causa di = because of, due to, more neutral
• grazie a = thanks to, positive

Examples:

• Per colpa del traffico, siamo arrivati tardi.
• A causa del traffico, siamo arrivati tardi.
• Grazie al bel tempo, siamo usciti.