Mercator ex Sicilia Brundisium navigat.

Mercator is nominative singular, which is the normal case for the subject of a sentence. It matches the verb navigat, which is he/she/it sails in the third person singular, so mercator is the one doing the action.

Also, mercator is a third-declension noun.

Ex is a preposition meaning out of or from, and it takes the ablative case. So Sicilia here is ablative singular: from Sicily.

This is a very common Latin pattern:

• ex
  • ablative = out of / from
• ab
  • ablative = from / away from
• in
  • ablative = in / on

Because Latin treats town names differently from larger places.

Brundisium is a town/city name, and with names of towns Latin usually expresses motion toward them without a preposition. So:

• Brundisium navigat = he sails to Brundisium

But Sicilia is a large island (and also a region/province), so Latin normally uses a preposition:

• ex Sicilia = from Sicily

So the contrast is very normal Latin:

• from Sicily
• to Brundisium

It is accusative singular, used here as the accusative of place to which.

With names of towns, Latin often uses the accusative by itself to show motion toward a place:

• Romam venit = he comes to Rome
• Brundisium navigat = he sails to Brundisium

Because Brundisium is a second-declension neuter noun. In neuter nouns, the nominative singular and accusative singular are the same form.

So:

• nominative: Brundisium
• accusative: Brundisium

That is why the ending does not visibly change here.

Navigat is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from navigo, navigare.

So it means he/she/it sails, is sailing, or sometimes more broadly travels by ship, depending on context.

Not in the ordinary sense. It is better understood as an accusative of place to which rather than a normal direct object.

English learners often see the accusative and think object, but Latin uses the accusative for several other functions too. Here Brundisium answers to where?, not what?

So this is not really:

• he sails Brundisium

It is:

• he sails to Brundisium

Yes. Latin word order is much freer than English word order, because the endings show the grammatical relationships.

So these could all mean essentially the same thing:

• Mercator ex Sicilia Brundisium navigat.
• Ex Sicilia mercator Brundisium navigat.
• Brundisium mercator ex Sicilia navigat.

The choice of order often changes emphasis, not basic meaning. In many Latin sentences, the verb also often comes near the end, as it does here.

Classical Latin normally prefers Brundisium navigat without a preposition, because Brundisium is a town name.

Using ad is not the usual basic construction here. In some contexts ad Brundisium can suggest something more like toward Brundisium or to the vicinity of Brundisium, though usage can vary.

So for a learner, the safest rule is:

• town name + accusative, no preposition for motion toward

Latin prepositions overlap somewhat, but they are not identical.

• ex often suggests out of / from within
• ab often suggests away from / from beside
• de often suggests down from, and it also has other uses such as about / concerning

For a simple idea like from Sicily, ex Sicilia is very natural. It fits especially well when someone is traveling out from a place.

They belong to three different declensions:

• mercator — third declension
• Sicilia — first declension
• Brundisium — second declension neuter

This matters because the declension tells you what endings to expect in different cases.

For example:

• Sicilia is first declension, so its ablative singular ends in -a: Sicilia
• Brundisium is second declension neuter, so nominative and accusative singular are both Brundisium
• mercator is third declension, so its nominative singular does not look like first- or second-declension nouns

Recognizing declensions helps you see why each word has the form it does.