Age and Duration Expressions

English uses “be” plus an adjective-like age—“she is ten years old”—and uses “for” before many durations. Classical Latin organizes both meanings differently. Completed age is most characteristically expressed by accusative years + nātus/nāta: decem annōs nāta “ten years old,” literally “born for ten years.” Duration is normally an accusative of extent: trēs hōrās exspectāvit “he waited for three hours.”

These are productive patterns, but neighboring formulas are not exact synonyms. A genitive such as puer decem annōrum describes “a boy of ten years”; sextum annum agit says that someone is living through the sixth year and has completed only five. Abhinc decem annōs places an event ten years ago. Learning the complete frame prevents the common mistake of translating “have twenty years” or “be twenty old” word for word.

The main frames

Completed age: annōs nātus or nāta

The standard conversational and narrative age formula combines an accusative measure with the perfect participle of nāscī, “be born.” Nātus agrees with a masculine subject, nāta with a feminine subject, and plural subjects require nātī or nātae. The number does not control that agreement.

The accusative annōs measures the interval since birth. It is not the direct object of “be born,” and Latin does not need an adjective corresponding to English “old.” Quot annōs? asks for the number because quot is an indeclinable numeral adjective; the answer retains the accusative frame.

A genitive of quality offers a more noun-centered description:

This genitive is especially natural inside a larger noun phrase or biographical description. It is (neutral/formal) rather than a different numerical fact. Puer duodecim annōrum and puer duodecim annōs nātus can describe the same age, but the former attributes a quality to “boy,” while the latter measures time from birth.

The year currently being lived: annum agere

Latin biographical prose can count the current year with an ordinal: sextum annum agit, literally “he is conducting his sixth year.” This is inclusive stage-counting, not the modern statement that six full birthdays have passed.

The distinction matters in historical ages. Vīcēsimō aetātis annō means “in the twentieth year of life,” whereas vīgintī annōs nātus means twenty full years old. Authors are not always trying to answer a modern form asking for completed age, so preserve the construction before converting the number.

How long? The accusative of duration

An ungoverned accusative can measure the temporal extent of a state or action. Ask quam diū? “for how long?” The answer may be a bare accusative noun phrase or an adverb such as diū “for a long time.”

The accusative measures the whole extension of exspectāvī, habitāvit, and manēbō. English supplies “for,” but Classical Latin ordinarily does not need a preposition. The ablative answers a different temporal question: eō annō means “in that year,” while eum annum with an appropriate verb can mean “for that year.” See Time Expressions for the location contrast.

Per plus the accusative is also Classical. It often makes traversal of the whole span explicit, especially when a modifier such as tōtus reinforces completeness.

The bare accusative is the unmarked answer to “how long?”; per tōtam noctem highlights continuity from one end of the night to the other. It is inaccurate to ban per, but equally inaccurate to insert it automatically every time English has “for.”

Virgil uses this extended-span frame in epic narrative; the quotation keeps source spelling rather than adding pedagogical macrons:

The separated order multos ... per annos is (literary) hyperbaton. Prose learners should normally keep per multōs annōs together.

Ago, before, and within

Abhinc looks backward from the speaker’s present: abhinc decem annōs “ten years ago.” Classical authors use it with either an accusative of extent or an ablative; the accusative is a clear productive model for learners. Ante decem annōs may also mean “ten years earlier/ago,” but ante can calculate from an explicit past reference point, whereas abhinc is anchored to “from now.”

A deadline is not a duration. The ablative of time within which says that the event will occur at some point inside the interval.

Compare paucōs diēs scrībam “I shall write for a few days,” where the accusative measures continuous writing. The English noun phrase looks similar, but case tells whether the interval contains the event or is filled by it.

A production diagnostic

1. To state completed age, use cardinal number + annōs nātus/nāta.
2. To describe a person as “of X years,” use X annōrum with a noun.
3. To identify the year of life currently in progress, use an ordinal with annum agere and subtract one for completed years.
4. To answer “how long?”, use the accusative of duration; add per when traversal or uninterrupted extent is genuinely prominent.
5. To say “ago” from now, use abhinc with an accusative or ablative measure.
6. To say “within” a period, use the ablative of time within which, not the duration accusative.

Common Mistakes

Copying “have twenty years” from another modern language

Forgetting agreement with the person

Using the ablative for an ordinary duration

Reading an ordinal year as completed age

Translating every English “for” with per

Key Takeaways

Completed age uses annōs nātus/nāta; a genitive in annōrum gives a descriptive age, and an ordinal with annum agere counts the year of life currently under way. Ordinary duration uses the accusative, while per emphasizes traversal of a span. Abhinc looks back from now, and the ablative can express completion within a deadline. The numeral alone never determines the meaning: the constructional frame does.