Accusative of Extent of Space

The accusative of extent of space measures how far, how long, how wide, how high, or how deep something reaches. In decem mīlia passuum prōgressī sunt “they advanced ten miles,” the accusative is not a destination and not a direct object: it lays out the spatial span of the advance. This is the spatial counterpart of the accusative of duration.

Measuring a movement

With a verb of movement, an accusative measurement answers quantum? “how far?”

English may say “walked for three miles,” but Latin needs no preposition for the measurement. The distance phrase is adverbial: it measures the event rather than naming something walked upon or toward.

Compare the three relations:

The English preposition “for” in the first translation does not correspond to Latin per. Conversely, per agrōs has a preposition because it names the terrain traversed, not because it measures its length.

The Roman mile: passūs and mīlia passuum

Roman distance expressions require special attention. A passus is a double pace, conventionally about 1.48 metres. One Roman mile is mīlle passūs, literally “a thousand paces.” With two thousand or more, mīlia is a neuter plural noun meaning “thousands,” and passuum becomes a partitive genitive:

In the second example, the whole phrase duo mīlia passuum expresses extent. Duo mīlia is accusative—the numeral agrees with the head noun mīlia—while passuum depends on mīlia as a genitive. Calling passuum accusative merely because the larger phrase has an accusative function produces a parsing error.

Dimensions of objects and places

The same case measures physical dimensions with adjectives such as longus “long,” lātus “wide,” altus “high/deep,” and crassus “thick.” The object described remains in whatever case its clause requires; the unit of measure is accusative.

In mūrus decem pedēs altus, mūrus and altus are nominative because they form the subject and its predicate adjective. Pedēs is accusative plural because it specifies the extent of the height. In fossam ... lātam, the ditch and adjective are accusative as the direct-object phrase, and pedēs is a second accusative with a different function. Matching endings do not make the two nouns one constituent.

The adjective altus covers both vertical directions: “high” when measured upward and “deep” when measured downward. Context determines the translation.

Distance from a reference point

Distance can be construed in two ways. When treated as a stretch of space, it is accusative:

When treated as the degree by which one position differs from another, Classical Latin can use the ablative of degree of difference, especially with spatial adverbs or comparatives:

The English translation may use “by” or omit it entirely. The Latin distinction is conceptual: accusative surveys the distance as an extent; ablative measures the difference between positions or values. See ablative of degree of difference.

A genitive of measure can also describe an object’s quality: vāllum duodecim pedum means “a rampart of twelve feet [in height].” This noun phrase characterizes the rampart, while vāllum duodecim pedēs altum explicitly supplies a dimension adjective and uses the accusative of extent. Both are Classical; they are not word-for-word variants with interchangeable endings.

Extent is not destination

An accusative without a preposition can mark direction with names of towns, small islands, domus, and rūs, while ordinary common nouns generally require ad or in. That construction answers “where to?”, not “how far?”

Rōmam is accusative of direction; centum mīlia passuum is accusative of extent. Their shared case does not make their functions identical. Latin cases encode several relations, and the verb, lexical class, modifiers, and meaning must all be considered.

Register and edge cases

Spatial extent is productive in (formal) historical and military prose, technical descriptions, itineraries, inscriptions, and ordinary practical measurement. Caesar naturally reports marching distances and ditch dimensions because those facts matter to narrative and engineering. Figurative language can extend the underlying image, as in the proverbial trānsversum unguem nōn discēdere, “not to depart a nail’s breadth,” where a tiny physical extent becomes a metaphor for moral deviation.

Latin measurement systems varied by period and setting. Converting pēs or passus into modern units can be helpful, but the syntax does not depend on an exact modern conversion. Preserve the Latin unit when precision or historical context matters.

Common Mistakes

1. Translating English “for” mechanically as prō

2. Confusing distance with destination

3. Making passuum accusative after plural mīlia

4. Matching the measure word to the described noun’s case

Key Takeaways

The accusative of spatial extent answers “how far?” or “how large in a stated dimension?” It measures movement and dimensions without requiring a preposition. Keep extent separate from destination and route, parse mīlia passuum internally as accusative plus partitive genitive, and distinguish accusative distance from an ablative degree of difference. The English translation may use “for,” “by,” or no preposition at all; the Latin relation determines the case.