Mare tranquillum est, et nauta e portu exit.

Because tranquillum is an adjective agreeing with mare.

• mare = sea
• tranquillum = calm

In Latin, adjectives must match the noun they describe in gender, number, and case.

Here, mare is:

• neuter
• singular
• nominative

So the adjective also has to be neuter singular nominative, which gives tranquillum.

Mare is nominative singular.

It is the subject of est, so it is the thing being talked about: the sea is calm.

A learner may expect a noun ending like -us or -a, but mare is a third-declension neuter noun. Its nominative singular form is simply mare.

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

So mare can mean:

• the sea
• a sea

Which one is best depends on context. In this sentence, English will usually translate it as the sea is calm, but Latin itself does not explicitly mark that distinction.

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

All of these can mean essentially the same thing:

• Mare tranquillum est
• Tranquillum mare est
• Est mare tranquillum

The endings show how the words fit together, so Latin does not rely as heavily on position as English does.

That said, Mare tranquillum est is a very natural and straightforward order:

• subject: mare
• predicate adjective: tranquillum
• verb: est

Latin often places the verb later in the clause.

Because some Latin nouns in the first declension are masculine, especially words referring to traditionally male occupations or roles.

Nauta means sailor, and it is one of those masculine first-declension nouns.

So you get forms like:

• nominative singular: nauta
• genitive singular: nautae

Even though the endings look like a typical feminine first-declension noun, the grammatical gender here is masculine.

Nauta is nominative singular.

It is the subject of exit:

• nauta exit = the sailor goes out

So in the sentence, there are two clauses joined by et:

1. Mare tranquillum est
2. nauta e portu exit

Each clause has its own subject and verb.

Portu is ablative singular.

The preposition e/ex means out of or from, and it takes the ablative case. So:

• e portu = out of the harbor / from the port

A very common thing to learn in Latin is that certain prepositions require certain cases. Here:

• e/ex + ablative

So portu must be ablative.

Because portus is a fourth-declension noun, not a second-declension noun.

Its basic forms are:

• nominative singular: portus
• ablative singular: portu

A learner might expect porto if thinking of second-declension forms such as servo or domino, but portus belongs to a different declension.

So after e/ex, the correct ablative singular is portu.

Both e and ex mean the same thing here: out of / from.

In many textbooks, you will often see:

• e before a consonant
• ex before a vowel or h

Since portu begins with p, e portu is perfectly normal.

However, Latin writers are not always completely rigid about this, and you may sometimes see ex before consonants too.

Yes. Latin exit is the verb form meaning he/she/it goes out or comes out.

It comes from exire:

• ex = out
• ire = to go

So:

• nauta e portu exit = the sailor goes out from the harbor

It is related to the English noun exit, but in Latin here it is a verb, not a noun.

Because the verb ending already tells you the person and number.

Exit is third person singular present active:

• he goes out
• she goes out
• it goes out

Since nauta is the subject, we understand:

• the sailor goes out

Latin often does not need an explicit subject pronoun like he or she, because the verb ending already gives that information.

It is present tense.

So it means:

• goes out
• is going out (depending on context)

If it were past tense, you would expect a different form, such as exiit for went out / has gone out.

So this sentence describes what is happening now:

• The sea is calm, and the sailor goes out from the harbor.

Et means and.

It joins the two clauses:

1. Mare tranquillum est
2. nauta e portu exit

So the sentence is made of two complete thoughts connected by et.

Latin et is very common and works much like English and.