One particular phenomenon I often encounter in foreign languages is their unusual treatments of the verb "to be". We tend to generalize things in English. But Spanish, for instance, differentiates between temporary states (like emotion or location) and permanent states (like a career, or a physical trait). Most language prefer "I have hunger" over our "I am hungry". And at least one language I know of (Russian) actually omits the verb "to be" completely from the sentence!
When in Rome...
In Italian, "being" is handled in a way that is somewhat similar to what I learned in Spanish, but different enough to require learning new rules. The verbs essere and stare both translate as "to be" in most uses, but they represent two different concepts which need to be understood in order to effectively communicate in Italian.
Stare actually means something more like "to stand" or "to stay". This is the ver to use with a gerund in the present and past continuous tenses, with an infinitive to describe something "just about to happen", or in a handful of idiomatic situations.
Come stai? - How are you?
Sto bene. - I am well.
Sto in piedi. - I am standing [on my feet].
L'uomo sta andando. - The man is walking.
Stavo per chiamare te. - I was just about to call you.
Essere is the verb that means "to be", and should be the one you instinctively choose in any situation not covered by the exceptions above. This would be the verb to describe an identity, a career, a classification, or a physical trait. It's is also appropriate for time of day and possession.
Io sono Eduardo. - I am Edward.
È un dottore? - Is he a doctor?
Tu sei cattolico. - You are a catholic.
Siamo Americani. - We are American.
Sono le sei. - It's six o'clock.
Questo è il libro di mia sorella. - This is my sister's book.
So basically, start with the expectation of using essere, unless you are constructing a continuous action using a gerund, describing something on the verge of happening, or in idiomatic expressions such as describing a person's mood or general state, in which you would use stare.
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