Li repagis la prunton sen ke li uzis krediton.

Repagis is the past tense of repagi, which means to repay or to pay back.

• pagi = to pay
• repagi = to pay back, repay

So Li repagis la prunton means he did not just make a payment; he repaid the loan.

The -n marks the direct object.

Here, the thing being repaid is la prunto = the loan. Since it is the direct object of repagis, it becomes la prunton.

This is very common in Esperanto:

• Li pagis la fakturon = He paid the bill.
• Li repagis la prunton = He repaid the loan.

La means the. It shows that we are talking about a specific, identifiable loan.

So la prunton suggests the loan, not just any loan in general.

Depending on context, prunton without la could also be possible, but la prunton is natural if the loan is already known from the situation or previous discussion.

Sen ke means without followed by a whole clause.

So:

• sen = without
• ke = that

Together, sen ke li uzis krediton means something like without him using credit or without the fact that he used credit.

It introduces a subordinate clause with its own verb.

Normally, no.

Sen already carries the negative idea of without, so sen ke li uzis krediton already means that he did not use credit.

If you add ne, the meaning can become confused or even reversed. So the usual form is:

• sen ke li uzis krediton

not

• sen ke li ne uzis krediton

For a learner, it is best to think: sen already does the negative work.

It is understandable, but many speakers would find sen uzi krediton more natural here.

Because the subject is the same in both parts of the sentence, Esperanto often prefers the infinitive:

• Li repagis la prunton sen uzi krediton.

That is a smoother way to say He repaid the loan without using credit.

Using sen ke is more useful when the subordinate clause has a different subject, for example:

• Li repagis la prunton sen ke lia frato helpis lin.

Here the second clause has a different subject, lia frato, so a full clause makes more sense.

It is repeated because sen ke introduces a full clause, and a full clause normally needs its own subject.

So:

• main clause: Li repagis la prunton
• subordinate clause: li uzis krediton

Even though both subjects are the same person, the second li is there because uzis is a finite verb in its own clause.

If you use the infinitive instead, you do not need to repeat the subject:

• Li repagis la prunton sen uzi krediton.

It is in the past because the whole situation is being described as a past event.

• repagis = repaid
• uzis = used

The sentence is saying that, in that past situation, he repaid the loan and did so without using credit.

Esperanto does not require a special tense here just because it is in a subordinate clause. The tense is chosen according to the meaning. Since the non-use of credit belongs to that same past situation, uzis is natural.

Not necessarily.

Kredito usually means credit in the financial sense, such as borrowed funds or access to borrowing. It does not specifically mean credit card.

If you want to say credit card, Esperanto normally uses kreditkarto.

So in this sentence, krediton most likely means he repaid the loan without using additional credit or borrowed money.