Suus or Eius? | Latin Grammar

English his, her, its, and their do not reveal whether the possessor is the clause’s subject. Latin normally does. Use suus, sua, suum when the third-person possessor is reflexive—typically the subject of the clause whose possession is being expressed. Use eius when one singular third-person referent already mentioned possesses something but is not that controlling subject. For plural non-reflexive possessors, Latin uses eōrum or eārum, not eius.

The key question is therefore not “Does English say his?” It is “Does this possession point back to the relevant subject or viewpoint-holder?” Once that is settled, inflection is separate: suus agrees with the thing possessed, whereas eius is a genitive pronoun and never agrees with that thing.

The basic subject test

In a simple finite clause, find the subject. If the possessor is that subject, choose suus. If the possessor is some other singular third person, choose eius.

Mārcus fīlium suum vocat.

Marcus calls his own son. (Marcus’s son)

Mārcus fīlium eius vocat.

Marcus calls his son. (another man’s or woman’s son)

This minimal pair is the core contrast. With suum, the possessive returns to the subject Mārcus. With eius, it points away from Marcus to an antecedent supplied by context.

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Draw an arrow from the possessor to the clause’s subject. If the arrow lands there, use suus. If it lands on another singular third-person referent, use eius. Do not decide from the English possessive.

Latin often omits a possessive when ownership is obvious, especially with body parts and close relations. Mārcus manum levat naturally means “Marcus raises his hand.” Suam may be added to contrast his own hand with someone else’s, but it is not obligatory merely because English has “his.”

Mārcus manum levat.

Marcus raises his hand. (the obvious possessor needs no possessive)

Mārcus manum suam, nōn meam, levat.

Marcus raises his own hand, not mine. (contrastive)

Agreement: look at the possession, not the possessor

Suus is a first/second-declension adjective. Its gender, number, and case come from the possessed noun. The owner can be male, female, singular, or plural without changing that agreement.

Iūlia fīliam suam laudat.

Julia praises her own daughter.

Iūlia fīlium suum laudat.

Julia praises her own son.

Mīlitēs arma sua reparant.

The soldiers repair their own weapons.

Here suam agrees with feminine fīliam, suum with masculine fīlium, and sua with neuter plural arma. None of those endings describes the owner. By contrast, eius has one fixed form because it is the genitive singular of is, ea, id.

Iūlia fīliās eius laudat.

Julia praises his or her daughters. (someone else’s)

The surrounding discourse must identify whether eius means “his,” “her,” or “its.” Latin does not encode that gender in eius itself.

Six minimal contrasts

Each pair changes only the possessor relation.

Rēx exercitum suum dīmittit.
The king dismisses his own army.
Rēx exercitum eius dīmittit.
The king dismisses that other person’s army.
Cornēlia cum amīcā suā ambulat.
Cornelia walks with her own friend.
Cornēlia cum amīcā eius ambulat.
Cornelia walks with his or her friend.
Puer librōs suōs invenit.
The boy finds his own books.
Puer librōs eius invenit.
The boy finds someone else’s books.
Senātōr sententiam suam dēfendit.
The senator defends his own opinion.
Senātōr sententiam eius dēfendit.
The senator defends the other person’s opinion.
Fēmina canem suum quaerit.
The woman is looking for her own dog.
Fēmina canem eius quaerit.
The woman is looking for his or her dog.
Legātī praemia sua accēpērunt.
The envoys received their own rewards.
Legātī praemia eōrum accēpērunt.
The envoys received those men’s rewards.

The sixth pair also shows the number distinction. Eius has a singular possessor; eōrum has masculine or mixed plural possessors, and eārum has feminine plural possessors.

A subordinate clause resets—or inherits—the viewpoint

In an ordinary subordinate clause, suus normally refers to the subject of that subordinate clause, not automatically to the subject of the main clause.

Mārcus gaudet quod Lūcius fīlium suum laudat.

Marcus is glad that Lucius praises his own son. (normally Lucius’s son)

Mārcus gaudet quod Lūcius fīlium eius laudat.

Marcus is glad that Lucius praises his son. (Marcus’s or another person’s son, not Lucius’s)

Reported thought creates an important extension. In indirect statement and many subjunctive clauses representing a person’s words, thought, purpose, or viewpoint, a reflexive may refer indirectly to the subject of the governing verb. This is the indirect reflexive.

Mārcus dīcit Lūcium fīlium suum laudāre.

Marcus says that Lucius praises his, Marcus’s, son. (indirect reflexive; context may need to disambiguate)

Because suum could also be understood locally as Lucius’s in an isolated sentence, good Classical prose relies on context or rewrites when ambiguity would matter. Eius can deliberately exclude the viewpoint-holder, but its antecedent must still be recoverable. The fuller system is explained under Indirect Reflexives and Logophoric Reflexives.

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In reported discourse, replace the simple “subject of this clause” test with “whose thought or purpose is being represented?” A reflexive can track that viewpoint-holder across subordination. This is a productive Classical pattern, not a poetic exception.

Suus can mean “one’s own” emphatically

Placed contrastively, suus stresses proper possession or what is characteristic of someone. The distributive phrase suus cuique means “to each his own.” Such uses are common in formal prose and maxims (formal/literary), but they still preserve reflexive or viewpoint-oriented force.

Suus cuique mōs est.

Each person has his own custom. (literally, ‘to each his own custom’)

Cīvēs sua dēfendunt.

The citizens defend what is their own.

Here sua is substantival neuter plural, “their own possessions/interests.” It does not become an invariant pronoun: its form still belongs to the adjective suus, sua, suum.

Short decision drill

“Claudia opens her own letter.” → suus: Claudia epistulam suam aperit. Claudia is subject and possessor; suam agrees with epistulam.
“Claudia opens his letter.” → eius: Claudia epistulam eius aperit. The singular possessor is not Claudia.
“The girls praise their own teacher.” → suus: Puellae magistrum suum laudant. The plural subject owns the relation; suum is masculine accusative singular because magistrum is.
“The girls praise those women’s teacher.” → eārum: Puellae magistrum eārum laudant. The possessors are feminine plural, so neither suus nor eius fits.
“Marcus says that the enemy fears him”—where “him” means Marcus—→ indirect reflexive: Mārcus dīcit hostem sē timēre. On the intended reported-viewpoint reading, sē refers to Marcus; because it can also be read locally as “himself,” context or a rewrite must resolve any real ambiguity.

Common Mistakes

1. Translating English “his” directly as eius

❌ Mārcus equum eius vendit.

Incorrect if Marcus sells his own horse: eius points away from the subject.

✅ Mārcus equum suum vendit.

Marcus sells his own horse.

2. Making suus agree with the owner

❌ Iūlia librum suam legit.

Incorrect: feminine Julia does not control the adjective’s gender.

✅ Iūlia librum suum legit.

Julia reads her own book; suum agrees with masculine librum.

3. Using eius for plural possessors

❌ Puellae domum eius vident.

Incorrect for ‘the girls see those women’s house’: eius has a singular possessor.

✅ Puellae domum eārum vident.

The girls see those women’s house.

4. Adding suus wherever English has a possessive

❌ Mārcus oculōs eius claudit.

Incorrect for ‘Marcus closes his eyes’: eius makes someone else the possessor.

✅ Mārcus oculōs claudit.

Marcus closes his eyes; possession is obvious and Latin normally leaves it unexpressed.

Always separate three decisions: whether possession needs expression, whether the possessor is reflexive or external, and what form the possessed noun requires.

Key Takeaways

Suus points to the relevant subject or viewpoint-holder; eius points to another singular referent.
Suus agrees with the possessed noun, while eius is invariant; plural outside possessors require eōrum/eārum.
Obvious possession often remains unexpressed, and reported discourse can license an indirect reflexive.

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