Pronouns

His, Her, and Their Controversy

When to use a pronoun and when to use a reflexive adjective

Cornêlia ê vîllâ suâ ambulat.
Flavia est amica eius.
sua and eius both mean her. What is the difference?

• Eius is the common, ordinary pronoun used to express ownership such as his/her field: agri eius.
• The plural is eôrum or eârum: agrî eôrum - their fields. It is the genitive form of is, ea, and id (he, she, and it); eius, genitive singular, means his, hers, or its. It is always the genitive form and is not specific.

• Sextus gave Marcus his book. Whose book is it?
• Sextus Marcô librum eius dedit. We are not sure whether the book belonged to Sextus or Marcus.

A more specific way is the third person reflexive adjective, (suus, sua, suum). This is used when one is expressing one's own as am emphatic difference from that of another or others. As an adjective it must agree with the noun it modifies: Sextus gave Marcus his book referring to Sextus' book (suum librum). Sextus Marcô suum librum dedit. Suum must refer to the subject. Now we know to whom the book had belonged. Since suus, sua, suum is referred to as a reflexive adjective, it reflects the subject of a sentence or clause.

Some examples from Cicero:
Paetus omnes libros quos frater suus reliquisset mihi donavit.
Paetus gave me all the books which HIS father had left (him understood)... whose brother - the brother of Paetus, the subject of the clause.
...hunc, sî secûtî erunt suî comitês.
...this man, if his (his fellow) companions follow...

My, Your, Our - these are easier to discern.. Meus frater ad suam cenam sero adveniet. My brother will arrive late at his dinner..whose dinner, the dinner of my brother, his own dinner. If I were to use eius here, I would be referring probably to some dinner previously mentioned such as: Gaius is giving a dinner party. Many will be there but knowing my brother, he will probably disturb his dinner party by arriving late. I hope Gaius will not be too angry with him. In this case, suam cannot be used because it is not the brother's dinner party but that of Gaius so the sentence would have eius.

Everyone should do his/her homework - eius - general

Everyone should do his/her own homework - suum - specific

And isn't it great that one word does it in Latin so we don't have the common misuse today of "Everyone should do their homework," using a plural possessive adjective when referring to a singular concept, simply because people fear using his as a generic adjective for both male and female forms?

^ Grammatica