Ventus aquam in piscina agitat.

Because aquam is the direct object of the verb. It is the thing being stirred.

The basic dictionary form is aqua, but in this sentence it has to be in the accusative singular, which for a first-declension noun is usually -am. So:

• aqua = nominative singular
• aquam = accusative singular

Ventus is in the nominative singular, which is the case normally used for the subject.

Latin often shows grammatical roles through endings rather than word order. So even if the words were rearranged, ventus would still be understood as the doer of the action because of its form.

Also, the verb agitat is singular, so it matches the singular subject ventus.

Here piscina is in the ablative singular because in is being used to show location: in the pool.

A very important Latin pattern is:

• in + ablative = in / on somewhere
• in + accusative = into / onto somewhere

So:

• in piscina = in the pool
• in piscinam = into the pool

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

So a noun like ventus can mean:

• the wind
• a wind
• sometimes just wind

Which one sounds best depends on context and translation choice.

The same is true for aquam and piscina.

Agitat is the third-person singular present active indicative form of the verb agitare.

That means it corresponds to he/she/it stirs, moves, agitates, or is stirring, depending on context.

Because the subject is ventus (wind), the sense is the wind stirs.

It can mean either one.

The Latin present tense often covers both:

• simple present: stirs
• present progressive: is stirring

English usually forces you to choose one, but Latin often leaves that distinction to context.

Putting the verb at the end is very common in Latin, although it is not required.

This sentence uses a very natural Latin order:

• Ventus = subject
• aquam = object
• in piscina = prepositional phrase
• agitat = verb

Because Latin uses case endings, the word order is more flexible than in English. A different order could still mean the same basic thing, though it might sound different in emphasis.

Yes, often they could.

For example, Latin could also say something like:

• Aquam ventus in piscina agitat
• In piscina ventus aquam agitat

The main meaning would stay the same because the endings still show each word's role.

However, changing the order can shift emphasis. Latin word order is not random; it is flexible, but meaningful.

They belong to two common declensions:

• ventus: second declension, masculine
• aqua: first declension, feminine
• piscina: first declension, feminine

So in this sentence you can see:

• ventus = nominative singular
• aquam = accusative singular
• piscina = ablative singular after in

In normal understanding, it describes the situation of the action: the wind is stirring the water in the pool.

In other words, it tells you where the water is being stirred.

A learner will usually understand in piscina as going with the whole event, not just sitting loosely next to one noun.