I say to my self --a becomes--- e ( for feminine) and-- o becomes --- i . And since it's a patriarchal society ... if you don't know assume it's masculine. And put that like , mankind ! -Man- When referring to groups of children it's Ragazz-i because there's BOTH boys and girls it has to be masculine (everyone!)
Yes, "sono" can mean "I am" or "they are", but because it is the verb "to be", everything that comes after the verb will tell you right away which one it is.
Sono una ragazza = I am a girl.
Sono ragazze = They are girls.
If it's singular, it has to be "I am".
If it's plural, it has to be "They are".
"To be" is irregular in all Indo-European languages. English has even fewer forms.
You can always tell the difference in Italian because the predicate must agree with the subject when there's a linking verb. Sono una ragazza = I am a girl. Sono ragazze = They are girls. If it's singular, you know it has to be "io" and if it's plural you know it has to be "loro".