Navicularius naulum et portorium numerat.

Because navicularius is in the nominative singular, the case normally used for the subject in Latin.

• navicularius = nominative singular
• It is a 2nd-declension masculine noun
• So it is the person doing the action

In this sentence, navicularius is the one who numerat.

They end in -um because they are neuter singular nouns of the 2nd declension.

In this sentence they are also accusative singular, the case used for direct objects. For 2nd-declension neuter nouns:

• nominative singular = -um
• accusative singular = -um

So the form looks the same in both cases.

That is why:

• naulum can be nominative singular or accusative singular
• portorium can be nominative singular or accusative singular

Here they are accusative singular because they receive the action of numerat.

We know from both case and verb agreement.

• The verb numerat is 3rd person singular
• So its subject is singular: navicularius
• naulum et portorium are in the accusative, which is the normal case for direct objects

Also, if naulum et portorium were the subject, we would expect a plural verb, not numerat.

So the structure is:

• navicularius = subject
• numerat = verb
• naulum et portorium = direct objects

Numerat is:

• present tense
• active voice
• indicative mood
• 3rd person singular

It comes from numerare.

So it means he/she/it counts, or in some contexts he/she/it pays out or reckons.

Because the subject is navicularius, the sense is the ship-owner / boatman / carrier counts or pays.

Latin usually has no articles.

So:

• navicularius can mean a ship-owner or the ship-owner
• naulum can mean a freight charge or the freight charge
• portorium can mean a harbor tax / customs duty or the harbor tax / customs duty

The context tells you whether English should use a, an, or the.

This is very normal in Latin and often feels strange to English speakers at first.

Yes and no.

The basic sense does not depend mainly on word order, because Latin uses case endings to show each word’s job. So these all mean essentially the same thing:

• Navicularius naulum et portorium numerat.
• Naulum et portorium navicularius numerat.
• Numerat navicularius naulum et portorium.

However, word order can affect emphasis.

In the original sentence:

• Navicularius comes first, so the sentence begins with the doer
• numerat comes last, which is a very common Latin pattern

So the order is natural and clear, even though other orders are possible.

Et simply means and.

It links the two direct objects:

• naulum
• portorium

So the verb applies to both of them:

• he counts/pays the freight charge
• and the port tax/customs duty

Yes. Literally, numerare means to count. But in financial contexts it can mean to count out money, and from there to pay.

English has something a little similar when we say someone counted out the money.

So depending on context, numerat may be understood as:

• counts
• reckons
• counts out
• pays

If your textbook gives a meaning like pays the freight and the port duty, that is perfectly reasonable.

Navicularius is a 2nd-declension masculine noun.

It is related to navicula, meaning small ship or boat. In usage, navicularius refers to someone connected with shipping, such as:

• a boatman
• a ship-owner
• a carrier by ship
• a shipping merchant

The exact English word depends on context.

So even if the meaning has already been given to you, it is useful to know that this is a person involved in transport by water.

They are both singular.

Even though there are two objects together, each noun itself is singular:

• naulum = singular
• portorium = singular

They are joined by et, so together they form a compound object: the freight charge and the port duty.

Because the verb agrees with the subject, not with the objects.

The subject is:

• navicularius = one person

So the verb is singular:

• numerat = he counts / pays

The two objects do not control the verb’s number.

No. This sentence has no adjectives.

All the main words except et are nouns or a verb:

• navicularius = noun
• naulum = noun
• portorium = noun
• numerat = verb
• et = conjunction

So there is no adjective here that needs to agree with a noun.

All three nouns are 2nd declension:

• navicularius = 2nd declension, masculine
• naulum = 2nd declension, neuter
• portorium = 2nd declension, neuter

That makes this sentence a useful example because it shows both:

• a masculine nominative singular in -us
• neuter accusative singular forms in -um

Not necessarily. A word-for-word translation like that is grammatically fine.

But whether it is the best translation depends on context, especially because numerat can have a financial sense. In a commercial setting, a smoother English translation might be:

• The ship-owner pays the freight and the port duty
• or The ship-owner reckons the freight and the customs charge

So the literal translation is useful for grammar, while the natural translation may be slightly different.