La ekzercon fininta studento sentas sin preta.

Fininta is the active past participle of fini (to finish).

It breaks down like this:

• fin- = the root finish
• -int- = active past participle, meaning having done or who has done
• -a = adjective ending

So fininta means having finished or who has finished.

In this sentence, la ekzercon fininta studento means the/a student who has finished the exercise.

Because ekzercon is the direct object of fini.

Even though fini appears here inside the participial form fininta, it still keeps its object just like a normal verb would:

• fini la ekzercon = to finish the exercise
• la ekzercon fininta studento = the student having finished the exercise

So the -n is there for the same reason it would be in a full clause such as:

• La studento finis la ekzercon.

In Esperanto, a participle can act like an adjective and still keep its own complements, including a direct object.

So la ekzercon fininta studento is a compact way of saying:

• la studento, kiu finis la ekzercon

Literally, the structure is something like:

• the exercise-having-finished student

This word order is normal in Esperanto, especially when the participle is directly attached to the noun it describes.

You could also express the idea with a relative clause, which may feel more natural to an English speaker:

• La studento, kiu finis la ekzercon, sentas sin preta.

Yes, in this sentence they are very close in meaning.

• la ekzercon fininta studento
• la studento, kiu finis la ekzercon

Both mean that the student completed the exercise.

The participle version is more compact. Also, -int- shows that the finishing happened before the main action or state in the sentence. So the student feels ready now, after finishing the exercise.

Because fininta and finita mean different things.

• fininta = having finished, who has finished
  This is active: the student did the finishing.
• finita = finished, having been finished
  This is passive: something else was finished.

So:

• fininta studento = a student who has finished
• finita ekzerco = a finished exercise

In this sentence, the student is the one performing the action of finishing, so fininta is the correct form.

Because the main statement is about the student’s current feeling:

• studento sentas sin preta = the student feels ready

The participle fininta shows an action that happened earlier than that:

• first: the student finished the exercise
• now: the student feels ready

So -int- does not necessarily mean a distant past. It means prior or already completed relative to the main situation.

Actually the sentence says sentas sin preta, not sintas.

The word sin is the reflexive pronoun, meaning himself / herself / themselves / oneself, depending on the subject.

Esperanto often uses the pattern:

• senti sin + adjective

So:

• Mi sentas min laca. = I feel tired.
• Li sentas sin feliĉa. = He feels happy.
• La studento sentas sin preta. = The student feels ready.

Literally, it is something like feels himself ready, but in normal English we just say feels ready.

Because the object refers back to the subject of the same clause.

The subject here is studento, so Esperanto uses the reflexive pronoun sin.

• La studento sentas sin preta. = The student feels ready.

If you used lin or ŝin, it would refer to some other person, not back to the student.

So sin is required because the student is both:

• the one who feels, and
• the one being described as ready

Because preta is a predicate adjective describing the subject’s state.

In senti sin preta, the idea is:

• the student feels
• himself/herself
• ready

So preta describes sin, which refers back to the subject studento.

Why not pretan?
Because this is not a normal direct-object adjective in the sense of a separate accusative noun phrase. In the common pattern senti sin + adjective, the adjective is normally just the plain adjective form:

• Mi sentas min bona.
• Ŝi sentas sin laca.
• Li sentas sin preta.

Why not prete?
Because prete is an adverb, which would modify the verb rather than describe the person’s state. Here we want ready as a quality of the student, so we use the adjective preta.

Grammatically, studento without la is usually a student, not explicitly the student.

So strictly speaking:

• La ekzercon fininta studento = a student who finished the exercise
• La studento, kiu finis la ekzercon = the student who finished the exercise

However, context can sometimes make English translators choose the student even when Esperanto leaves the noun indefinite.

A learner should notice that the la in this sentence belongs to ekzercon:

• la ekzercon = the exercise

It does not automatically make studento definite.

The la directly marks ekzercon as definite:

• la ekzercon = the exercise

It does not directly mark studento.

So the phrase is structured like this:

• la ekzercon = the exercise
• fininta = having finished
• studento = student

That gives:

• the exercise-having-finished student

In more natural English: a/the student who has finished the exercise, depending on context.

If you wanted to clearly say the student, you would normally put la with studento:

• La studento, fininta la ekzercon, sentas sin preta.

Yes. A very natural expanded version is:

• La studento, kiu finis la ekzercon, sentas sin preta.

Or, if you want to avoid making the student definite:

• Studento, kiu finis la ekzercon, sentas sin preta.

The original sentence is just a more compact participial version. Esperanto uses this kind of structure much more freely than English does.

It helps to divide it into parts:

• La ekzercon fininta studento = the student / a student who has finished the exercise
• sentas = feels
• sin preta = himself/herself ready

So the whole sentence says:

• [Subject] the student who finished the exercise
• [Verb] feels
• [Complement] ready

This is a good example of three common Esperanto features working together:

1. a participle used like an adjective (fininta)
2. accusative marking inside that participial phrase (ekzercon)
3. the reflexive pattern senti sin + adjective (sentas sin preta)