Soror respondet se Corinthum ire velle, antequam Romam redeamus.

This is an indirect statement after respondet.

A useful way to divide it is:

• se = the subject of the indirect statement
• velle = the main infinitive of the indirect statement, to want
• Corinthum ire = an infinitive phrase depending on velle, to go to Corinth

So the core pattern is:

• respondet
  • se ... velle
    = she answers that she wants ...

And then:

• ire depends on velle
  = wants to go

So literally the structure is something like:

• The sister answers herself to want to go to Corinth

That sounds awkward in English, but it is normal Latin grammar for the sister answers that she wants to go to Corinth.

Because se is the reflexive pronoun. It refers back to the subject of the main verb, here soror.

Latin uses se for:

• himself
• herself
• itself
• themselves

So se does not show gender.

Why not eam? Because eam would mean her, referring to some other female, not back to the subject herself.

So:

• soror respondet se ire velle = the sister answers that she wants to go
• soror respondet eam ire velle = the sister answers that she/another woman wants to go

Because Latin often uses an accusative-and-infinitive construction instead of a that-clause.

In English we say:

• She answers that she wants to go

In Latin, a very common pattern is:

• main verb of saying/thinking/perceiving
• then accusative subject + infinitive

So:

• respondet se ... velle

literally works like:

• she answers herself to want ...

but in good English it means:

• she answers that she wants ...

So the idea of that is present, but Latin expresses it with grammar rather than with a separate word.

Because the sentence contains one idea inside another:

• velle = to want
• ire = to go

Latin says:

• se ... velle = that she wants
• ire = what she wants to do

So ire is the complement of velle.

In English we also often use two infinitives:

• she wants to go

Latin is doing the same thing, except that the whole statement is also inside indirect speech:

• respondet se ire velle
  = she answers that she wants to go

Because with names of cities (and some similar place words), Latin often uses the accusative of place to which with no preposition after a verb of motion.

So:

• Corinthum ire = to go to Corinth
• Romam redire/redeamus = to return to Rome

English needs to, but Latin does not here.

This is especially common with:

• names of cities
• names of small islands
• a few special words like domum = home

So a learner should recognize:

• Romam = to Rome
• Athenas = to Athens
• Carthaginem = to Carthage

They are accusative singular.

That may look surprising at first, because in English a destination is often introduced by a preposition, but Latin commonly uses the accusative by itself for motion toward a city.

So here:

• Corinthum = accusative, destination after ire
• Romam = accusative, destination after redeamus

This is not the object of the verb in the ordinary English sense. It is the special Latin use called accusative of place to which.

Redeamus is present subjunctive, first person plural: we may return / we return in this kind of clause.

After antequam (before), Latin often uses the subjunctive when the action is viewed as anticipated, not yet completed, or future from the point of view of the sentence.

Here the returning to Rome is something still ahead:

• she wants to go to Corinth before we return to Rome

So the subjunctive fits that forward-looking idea.

Also, because this clause is part of reported content, the subjunctive is especially natural.

The -mus ending already means we.

Latin verb endings usually include the subject, so a separate pronoun is often unnecessary.

So:

• redeamus = we return / let us return / we may return depending on context

If Latin wanted to add nos, it would usually be for emphasis:

• nos redeamus = we return, as opposed to someone else

But here plain redeamus is enough.

Velle is a present infinitive.

In indirect statement, the tense of the infinitive is usually relative to the main verb, not simply absolute in time.

So:

• respondet = she answers
• velle = her wanting is simultaneous with the answering
• ire = the going is what she wants to do; it is dependent on that wanting

Even though the actual going may happen later, Latin still uses the present infinitive with velle, because it expresses the action as connected with the present desire.

So ire velle is the normal way to say:

• to want to go

Yes. Latin word order is much more flexible than English word order.

This sentence puts the parts in a fairly natural order:

• Soror respondet = main statement first
• se Corinthum ire velle = the content of what she answers
• antequam Romam redeamus = the time clause at the end

Latin could rearrange many of these words without changing the basic meaning, because the endings show the grammar.

For example, Corinthum ire is a very normal order, with the destination before the verb of motion.

So the word order here is not something you have to translate mechanically into English order; it is just one natural Latin arrangement.

Because Latin has no articles.

So soror can mean, depending on context:

• the sister
• a sister
• simply sister

You have to decide from context which English article is best.

That is normal throughout Latin:

• puella = the girl or a girl
• rex = the king or a king

So nothing is missing here; Latin simply does not use articles the way English does.