"They are girls."
Translation:Loro sono ragazze.
"Sono" can have the context of either "I" or "They". The context is made clear here by "Ragazze", the plural of girls. Therefore, "I am girls" cannot be correct. The only possible meaning for "Sono ragazze" is therefore "They are girls". "Loro sono ragazze" is gramatically correct also but the "Loro" is not a requirement given the rest of the phrase.
Given the lesson, the example had been "Loro sono donne" = They are women. So, in this instance wouldn't Loro ragazze have been correct also? I am still trying to grasp the difference between Loro and sono since the translation of sono is are with they in parentheses. Is Loro a more formal way of speaking?
Loro is the word that can be dropped- so you could say "Sono ragazze" and we would still know what it means without 'loro'. Even though 'sono' could mean both 'I am' or 'they are' we would know which one to use if the word is used earlier in the passage. There's no need to repeat 'loro' if it's already been said and we know who they're talking about.
Loro sono ragazze = They are girls.
Sono ragazze = They are girls.
Loro ragazze = They girls. (incorrect)
There's not much to explain. You can drop the loro because it's obvious from sono ragazze.
Sono ragazza, siamo ragazze
Sei ragazza, siete ragazze
È ragazza, sono ragazze
All good sentences.