I'm confused, what about https://forum.duolingo.com/comment/422836 ?
Is it incorrect to say "nous mangeons son riz" for "we eat his rice"? Or is there some rule which makes it okay when speaking about a group you're a part of, but not okay when speaking of others (like in "elle mange sa banane")?
In that sentence, the possessive would be different if it were our rice: "Nous mangeons notre riz." The rule only applies when the possessive would be the same, so with his, her, and its (son, sa, ses). Otherwise, the different possessive gives the context that the object belongs to someone else:
- Elle/Il mange ma banane - She/He is eating my banana
- Elle/Il mange ta banane - She/He is eating your banana
- Elle mange sa banane - She is eating her banana
- Elle mange sa banane à lui - She is eating his banana
The object is the item owned. The owner is represented by a possessive adjective (my, your, etc.) describing the object.
If the owner is "je", "tu", "nous", or "vous", you don't need to specify, because each of those has its own possessive adjective, "ma/mon/mes", "ta/ton/tes", "notre/nos", and "votre/vos", respectively.
When it's complicated is when the owner is "il" or "elle". In this case it depends on who the subject of the sentence is. Let's use the sentence we have already, "She is eating her banana", as an example, assuming no context.
In this sentence, "she" (elle) is the subject, the one doing the eating. The banana is the object, the thing being eaten. The owner is "her", the same person as is doing the eating (in other words, the owner is also the subject), so no need to specify in the French - it will be translated as "Elle mange sa banane".
If you change the sentence to "She is eating his banana", then "she" is still the subject and the banana is still the object, but the owner has changed to "his", a different person from the one doing the eating (in other words, the owner is not also the subject). In that case, you do need to specify.
Does that answer your question?
Hi Trofaste, I too tried for curiosity "his banana" and learned something here with your answer: "In French, the object conventionally belongs to the subject. Because "she" is the subject, therefore, the banana is assumed to be hers." Just thought you'd want to know.