Quia ventus crescit, nautae e portu celeriter discedunt.

Quia means because and introduces a clause giving the reason for the main action.

So the sentence is structured like this:

• Quia ventus crescit = Because the wind is rising / growing stronger
• nautae e portu celeriter discedunt = the sailors quickly leave the harbor

It is a very common way to introduce a reason in Latin.

Ventus is the subject of crescit, so it is in the nominative singular.

• ventus = wind
• crescit = grows / increases / rises

Since the wind is the thing doing the action, nominative is the correct case.

Crescit literally means grows or increases. With ventus, a natural English translation is often:

• the wind is rising
• the wind is getting stronger
• the wind increases

Latin often uses a simple verb where English prefers a slightly more idiomatic expression.

Nautae is nominative plural, meaning sailors.

It is the subject of discedunt:

• nautae = the sailors
• discedunt = leave / depart

A learner may notice that nauta is a first-declension noun but refers to a male profession. That is normal in Latin: some first-declension nouns are masculine, especially words like nauta (sailor) and poeta (poet).

The preposition e (or ex) means out of or from, and it takes the ablative case.

So:

• e = out of / from
• portu = ablative singular of portus (harbor, port)

Together, e portu means out of the harbor or from the harbor.

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

In many textbooks, you will see this guideline:

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

Since portu begins with a consonant, e portu is very natural. But Latin authors can sometimes use either form.

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

Its forms include:

• nominative singular: portus
• ablative singular: portu

So after e/ex, you need the ablative, which is portu.

This is a very common thing for learners to notice, because portus looks a bit like a second-declension noun at first glance, but it is actually fourth declension.

Celeriter is an adverb, meaning quickly.

It modifies the verb discedunt:

• celeriter discedunt = they leave quickly

It is not an adjective because it is not describing a noun like sailors; it is describing how they leave.

The related adjective is celer, celeris, celere = quick.
From that adjective, the adverb celeriter is formed.

Discedunt means they depart, they leave, or they go away.

It is:

• third person plural
• present tense
• from discedo, discedere

Because the subject is nautae (the sailors), the plural verb discedunt is required.

Latin word order is much more flexible than English word order because the endings show the grammatical roles.

Putting the verb at or near the end is very common in Latin, especially in straightforward prose. So:

• nautae e portu celeriter discedunt

is perfectly normal Latin word order.

English usually needs a more fixed order, but Latin does not.

Yes. Latin present tense can often be translated in more than one way depending on context.

So crescit could be:

• grows
• is growing
• is rising

And discedunt could be:

• leave
• are leaving
• depart

English chooses between simple present and progressive more often than Latin does.

Latin has no articles, so it does not have separate words for the or a/an.

That means:

• ventus can mean wind, the wind, or a wind
• nautae can mean sailors or the sailors
• portu can mean harbor or the harbor in context

English has to supply the article when translating, but Latin does not.

The comma separates the subordinate clause from the main clause:

• Quia ventus crescit = subordinate clause of reason
• nautae e portu celeriter discedunt = main clause

In English, we also often use a comma when a dependent clause comes first. In Latin manuscripts, punctuation was not always used the same way as in modern printed texts, but in modern editions and textbooks this comma is very normal.

Here quia introduces a reason that is presented as a straightforward fact, so crescit is in the indicative.

That is the normal construction for a simple factual statement:

• Quia ventus crescit... = Because the wind is rising...

In some kinds of Latin, especially in more advanced texts, clauses with quia and other conjunctions can show more subtle choices of mood, but for a sentence like this, the indicative is exactly what you would expect.