are
The word 'sono' is the Italian equivalent of the English word 'are'. It is used as a linking verb to connect the subject with a predicate. For example, 'Le mele sono rosse' means 'The apples are red'. It is important to note that 'sono' changes according to the number and gender of the subject. For example, 'Lui è' (He is) and 'Lei è' (She is) are used for singular subjects, while 'Sono' is used for plural subjects.
I am happy.
In this sentence, 'sono' is used to express the state of being. It is the first person singular form of the verb 'essere' (to be) in Italian. So 'Sono Felice' translates to 'I am happy' in English.
It's eight o'clock.
Here, 'sono' is used to tell the time. In Italian, you use 'sono le' for telling the time when the hour is more than one. Therefore, 'Sono le otto' means 'It's eight o'clock'.
I am from Rome.
In this phrase, 'sono' is used to express origin or where one comes from. It is the first person singular form of the verb 'essere' (to be) in Italian. So 'Sono di Roma' translates to 'I am from Rome' in English.