Navis oneraria postridie proficiscitur.

Navis means ship, and oneraria means cargo-carrying or for carrying loads.

Together, navis oneraria means a cargo ship, a merchant ship, or a transport vessel.
It contrasts with something like a warship.

The adjective oneraria comes from onus, oneris, meaning load or burden.

Here navis is nominative singular.

That makes sense because it is the subject of the sentence, and the verb proficiscitur is also singular, so the sentence is talking about one ship.

A beginner may notice that navis can also be genitive singular in other contexts, but here the verb and the rest of the sentence show that it must be nominative singular.

Because it agrees with navis, and navis is a feminine noun.

In Latin, adjectives must agree with the nouns they describe in:

• gender
• number
• case

So since navis is feminine singular nominative, oneraria is also feminine singular nominative.

Here it is an adjective modifying navis.

So:

• navis = ship
• oneraria = cargo-carrying

However, in some contexts Latin can use an adjective by itself as a noun. So oneraria by itself can sometimes mean cargo ship. But in this sentence it is clearly functioning as an adjective with navis.

Postridie means on the next day or the following day.

It is an adverb, so it tells you when the action happens.

It does not mean exactly the same thing as tomorrow.
For tomorrow, Latin normally uses cras.

Postridie usually means the day after some previously mentioned day.

Because proficiscor is a deponent verb.

Deponent verbs:

• have passive forms
• but active meanings

So proficiscitur looks like a passive form because of the ending -tur, but it means he/she/it sets out, departs, or starts a journey.

This is very common in Latin, and proficiscor is one of the standard deponent verbs learners meet early.

Proficiscitur is:

• present tense
• indicative mood
• third person singular

So it means he/she/it sets out or departs.

Because the subject is navis oneraria, the natural English translation is the cargo ship departs or the cargo ship sets out.

Because proficiscor is normally intransitive.

That means it describes an action that does not take a direct object. A ship can depart or set out, but it does not depart something.

So the sentence is complete with just:

• the subject: navis oneraria
• the time word: postridie
• the verb: proficiscitur

Latin does not have articles like English the and a/an.

So navis oneraria can mean:

• a cargo ship
• the cargo ship

Which one is best depends on the context.

English has to choose an article, but Latin usually leaves that idea to be understood from the situation.

Latin word order is much more flexible than English word order.

This sentence is arranged in a very natural Latin way:

• navis oneraria = the subject first
• postridie = the time expression
• proficiscitur = the verb at the end

Putting the verb at the end is especially common in Latin.

The order helps the sentence feel clear and orderly, but Latin could move these words around for emphasis without changing the basic meaning.