Postea discipuli de fabula inter se disputant, et magistra rogat cur ita disputent.

Discipuli is nominative plural, so it means the students and serves as the subject of disputant.

Its dictionary form is discipulus, discipuli, meaning student or pupil. In the plural nominative, a second-declension masculine noun ends in -i, so discipuli = the students.

Postea means afterward, later, or after that. It is an adverb, so it does not change form.

It tells you when the action happens:

• Postea discipuli ... disputant = Afterward the students discuss ...

Latin word order is flexible, so postea is placed first here for a natural time-setting effect.

The preposition de means about or concerning, and it takes the ablative case. That is why fabula appears in the ablative singular.

So:

• fabula can be nominative or ablative singular depending on context
• after de, it must be understood as ablative

Thus de fabula = about the story

Inter se means among themselves or with one another.

Here:

• inter normally means among or between
• se is the reflexive pronoun meaning themselves

So discipuli inter se disputant means the students are discussing among themselves, rather than speaking to the teacher.

Disputant is present tense, third person plural, active voice.

It comes from disputo, disputare, meaning to discuss, debate, or argue.

So:

• disputant = they discuss or they are discussing

Latin present tense can often be translated either as simple present or present progressive in English, depending on context.

Disputent is present subjunctive, third person plural, from the same verb disputare.

So:

• disputant = indicative, ordinary statement of fact: they are discussing
• disputent = subjunctive, used here in an indirect question: why they are discussing

This is a very common Latin pattern:

• a verb like rogat introduces a question indirectly
• the verb inside that indirect question goes into the subjunctive

That is why the sentence has:

• main statement: discipuli ... disputant
• indirect question: cur ita disputent

Because cur ita disputent is an indirect question.

In Latin, indirect questions regularly use the subjunctive. The direct version would be something like:

• Cur ita disputatis? = Why are you discussing like that?

But once that question is reported indirectly after rogat:

• magistra rogat cur ita disputent = the teacher asks why they are discussing like that

So the subjunctive is not showing doubt here. It is mainly there because Latin grammar requires it in indirect questions.

Cur means why.

It introduces a question, either:

• direct: Cur...? = Why...?
• indirect: rogat cur... = she asks why...

In this sentence it introduces an indirect question, which is why the verb after it is subjunctive: disputent.

Ita means thus, so, or in that way.

In this sentence, cur ita disputent means:

• why they are arguing/discussing like that
• why they are discussing in that way

It describes the manner of the discussion.

Magistra is also nominative because it is the subject of the second verb, rogat.

So the sentence has two coordinated clauses:

• discipuli ... disputant = the students discuss
• magistra rogat ... = the teacher asks ...

Even though English often repeats subjects less explicitly, Latin makes the subject of each clause clear by case and verb ending.

Rogat is present tense, third person singular, active voice, from rogo, rogare.

It means she asks here, because the subject is magistra, which is feminine.

So:

• magistra rogat = the teacher asks

Like disputant, it is in the present tense.

Latin word order is much more flexible than English because grammatical roles are shown mostly by endings, not by position.

For example:

• discipuli is clearly the subject because of its nominative plural ending
• de fabula is clearly a prepositional phrase
• magistra is the subject of rogat
• disputent is inside the indirect question introduced by cur

So Latin can arrange words for emphasis or style. This sentence is quite natural:

• time word first: Postea
• then subject and action
• then a second clause with et

English depends much more heavily on word order to show who is doing what.

The indirect question is:

• magistra rogat cur ita disputent = the teacher asks why they are discussing like that

A direct question would be something like:

• Cur ita disputatis? if the teacher is speaking directly to the students
• or Cur ita disputant? if someone is asking about them

The important change is that the indirect question uses the subjunctive:

• disputent

But the direct question normally uses the indicative:

• disputatis or disputant, depending on who is being addressed or described.