Portorium magnum debitorem impedit quominus pecuniam persolvat.

The main verb is impedit, meaning hinders / prevents.

Its subject is portorium magnum.

So the core structure is:

portorium magnum = the thing doing the hindering
impedit = hinders
debitorem = the person being hindered

Everything after quominus explains what the debtor is being prevented from doing.

Because magnum agrees with portorium.

• portorium is neuter singular nominative
• the adjective magnus, -a, -um must match it in gender, number, and case
• so the correct form is magnum

This is a basic agreement pattern in Latin adjectives:

• magnus for masculine singular nominative
• magna for feminine singular nominative
• magnum for neuter singular nominative

Debitorem is accusative singular.

It is in the accusative because it is the direct object of impedit. In other words, it is the person whom the tax hinders.

Its dictionary form is debitor, debitoris = debtor.

So:

• debitor = nominative singular
• debitorem = accusative singular

After verbs of hindering, preventing, restraining, stopping, Latin often uses quominus + subjunctive.

So with impedit, a very common pattern is:

aliquem impedit quominus...
= he prevents someone from...

In English we usually say prevents someone from paying, with from + -ing.
Latin often expresses that idea with quominus instead.

So quominus here is not something you should try to translate word-for-word every time; it is part of a standard construction.

Because it is inside a quominus clause after a verb of hindering.

After impedit quominus, Latin normally uses the subjunctive, so persolvat is not subjunctive because the action is doubtful in the English sense; it is subjunctive because the grammar of the construction requires it.

Here persolvat is:

• present
• subjunctive
• active
• 3rd person singular

Because the main verb impedit is in a primary tense (present), and the subordinate clause follows normal sequence of tenses.

So Latin uses the present subjunctive for an action that is simultaneous with or subsequent to the main verb:

• impedit = is hindering
• persolvat = that he pay / from paying

This is the expected tense after a present main verb in this kind of clause.

The understood subject of persolvat is the debtor: debitorem.

English often repeats the person more explicitly, but Latin does not need to. Once debitorem has been introduced as the person being hindered, it is natural to understand that he is the one who would do the paying.

So the sense is:

• the large tax hinders the debtor
• from his paying the money

Pecuniam is the direct object of persolvat.

It is accusative singular of pecunia, meaning money.

So in the subordinate clause:

• persolvat = pay
• pecuniam = the money

That gives the idea pay the money or settle the amount due.

The verb here is persolvat, from persolvere, not just solvere.

The prefix per- often adds a sense of completeness. So persolvere can mean:

• pay in full
• pay off
• discharge completely

So this sentence may suggest not merely make a payment, but settle the debt fully.

Portorium usually refers to a customs duty, toll, or tax on goods.

So depending on context, it could be understood as:

• a tax
• a tariff
• a customs charge
• a toll

A learner should know that it is not just any abstract fee; it often has a more specific commercial or governmental sense.

Because Latin and English build this idea differently.

English says:

• prevent someone from paying

Latin often says:

• aliquem impedire quominus solvat/persolvat

So instead of a preposition like from plus an -ing form, Latin uses:

• a person in the accusative
• then quominus
• then a subjunctive verb

This is just one of those patterns that has to be learned as an idiom.

The word order could be rearranged, because Latin word order is fairly flexible.

This sentence is orderly and natural:

Portorium magnum | debitorem | impedit | quominus pecuniam persolvat

A few effects of the chosen order:

• Portorium magnum comes first, so the obstacle is introduced immediately.
• debitorem appears before the clause that explains what he is prevented from doing.
• persolvat comes at the end of its clause, which is very common in Latin.

So the order is not random, but it is not as rigid as English word order either.