Debitor pecuniam persolvit.

Because pecuniam is in the accusative singular. In this sentence, it is the direct object of persolvit, so it shows the thing being paid.

The basic form is pecunia. Its forms are:

• nominative singular: pecunia
• accusative singular: pecuniam

A native English speaker often expects word order to show the object, but in Latin the ending is what matters most.

Debitor is nominative singular, because it is the subject of the sentence: the person doing the action.

Its accusative singular would be debitorem, but that would make it the direct object instead.

So here:

• debitor = the debtor, as subject
• pecuniam = the money, as object

You know mainly from the case endings, not from position alone.

In this sentence:

• debitor is nominative, so it is the subject
• pecuniam is accusative, so it is the object

That means the debtor is the one paying, even if the words were rearranged. For example, Pecuniam debitor persolvit would still mean the same thing.

Latin normally has no articles. It does not have separate words that exactly match English the or a/an.

So debitor can mean:

• the debtor
• a debtor

And pecuniam can mean:

• the money
• some money

Which one is best depends on context.

This is a very common question, because persolvit can be ambiguous.

It can be either:

• present tense: he/she pays
• perfect tense: he/she paid or has paid

This happens because some third-conjugation verbs have the same form in the 3rd person singular present and the 3rd person singular perfect.

So you usually tell from context. If your book already gives one meaning, follow that meaning there.

The dictionary form is persolvo, persolvere, persolvi, persolutus.

From that verb:

• persolvit can be present 3rd singular
• persolvit can also be perfect 3rd singular

The ending -t tells you it is he/she/it.

Because the verb ending already includes the subject person and number.

In persolvit, the -t shows 3rd person singular:

• he pays
• she pays
• it pays
• or, in the perfect, he/she/it paid

Latin often leaves out subject pronouns unless they are needed for emphasis or contrast.

There is often a slightly stronger sense than plain solvit.

The prefix per- can add the idea of doing something completely or through to the end. So persolvere often means:

• to pay in full
• to discharge completely
• to settle

Depending on context, Debitor pecuniam persolvit may suggest that the debtor fully pays or settles the money owed.

Yes, often it can.

Because Latin uses endings to show grammatical function, these can all mean basically the same thing:

• Debitor pecuniam persolvit
• Pecuniam debitor persolvit
• Persolvit debitor pecuniam

However, changing the order can change emphasis. For example:

• putting pecuniam first may emphasize the money
• putting persolvit first may emphasize the action

So word order in Latin is flexible, but not meaningless.

Yes, pecunia is a very common Latin word for money, cash, or wealth.

In this sentence, pecuniam is just the accusative singular form required by the verb.

Depending on context, it could refer to:

• money in general
• a sum of money
• payment owed

Debitor is a second-declension masculine noun.

Its nominative singular ends in -or, which is normal for some second-declension masculine nouns.

Pecunia is a first-declension feminine noun.

So the two nouns belong to different declensions:

• debitor, debitoris? Wait—actually for full accuracy, debitor is a third-declension-looking shape but it is in fact a noun whose nominative ends in -or and whose genitive is debitoris. So it is better understood as a third-declension noun.
• pecunia, pecuniae is first declension

A learner may expect all masculine nouns ending in -or to work one way, but the safest approach is always to learn the dictionary form and genitive.

It is third declension: debitor, debitoris.

This is worth correcting carefully, because English speakers often associate masculine nouns with the second declension, but -or nouns like debitor belong to the third declension.

That means:

• nominative singular: debitor
• accusative singular: debitorem
• genitive singular: debitoris

By contrast, pecunia, pecuniae is first declension.

Yes. It is short, straightforward, and very normal for a teaching sentence.

It has:

• a nominative subject: debitor
• an accusative direct object: pecuniam
• a finite verb: persolvit

So it is a good example of a basic Latin sentence pattern, even though the verb form itself is slightly tricky because of the present/perfect ambiguity.