The Italian word siccome (seek-koh-mai) started being used in the second half of the 13th century, and is the union of two other Italian adverbs, sì and come. It must have become popular immediately, as even Dante and Petrarca used it!
Siccome functions as a subordinating conjunction used to introduce a reason or cause, much like the English equivalent of “since” or “because.” Its use is predominantly found at the beginning of a sentence, unlike “perché,” which can also appear in the middle of sentences: so you say: siccome parlo Francese, chiamerò io l’albergo (“as I speak French, I’ll call the hotel myself”), but chiamerò io l’albergo, perché parlo Francese, which translates the same way.
As we said, siccome has been part of Italian usage for centuries, and helps establish causal relationships between events or actions. It is formal but still commonly used in both written and spoken Italian. However, the use of siccome is preferred in situations where the cause is already known or obvious to the listener or reader. For example, in the sentence siccome piove, non andiamo al parco, which translates to “Since it’s raining, we’re not going to the park,” the cause (rain) is known and directly related to the decision not to go to the park.
Siccome differs slightly from other Italian causal conjunctions like dato che or poiché, as it often carries a more straightforward and neutral tone: indeed, it is used when the speaker wants to establish a clear, factual reason without added emphasis.
Siccome ero stanco, sono andato a letto presto.
Since I was tired, I went to bed early.
Siccome non ho i soldi, non posso comprare quel libro.
Since I don’t have the money, I can’t buy that book.
Siccome avevo già mangiato, non ho preso nulla al ristorante.
Since I had already eaten, I didn’t order anything at the restaurant.