Pater in tablino sedet et epistulas legit, dum filia in horto ludit.

Pater is nominative singular, the case used for the subject of the verb. In this sentence, the father is the one who sits and reads, so pater is the correct form.

The same idea applies to filia: it is also nominative singular, because the daughter is the subject of ludit.

After in, Latin uses:

• ablative for location: in the study, in the garden
• accusative for motion into: into the study, into the garden

So:

• in tablino = in the study
• in horto = in the garden

Because nobody is moving into these places, Latin uses the ablative.

Tablino comes from tablinum, a neuter second-declension noun. In this sentence it is ablative singular, because it follows in with the meaning of location.

A tablinum in a Roman house was a kind of study, office, or reception room.

Epistulas is accusative plural, because it is the direct object of legit: these are the things the father reads.

Compare:

• epistulae = letters as a subject, or of the letter / to the letter depending on context
• epistulas = letters as a direct object

So epistulas legit means he reads letters.

Latin has no articles like English the or a/an. So a word like pater can mean:

• the father
• a father
• sometimes simply father

The exact meaning depends on the context. In a simple story like this, English often translates it as the father and the daughter.

Dum here means while.

It introduces an action happening at the same time as the action in the main clause:

• Pater ... legit = the father reads
• dum filia ... ludit = while the daughter plays

So dum links two simultaneous actions.

The verbs are:

• sedet = sits / is sitting
• legit = reads / is reading
• ludit = plays / is playing

Latin often uses the present tense where English could use either:

• a simple present: reads
• or a progressive present: is reading

In this sentence, the idea is that these actions are going on at the same time, so English often translates them with is sitting, is reading, is playing.

Yes, in form alone legit can be ambiguous:

• legit can mean he/she reads (present)
• lēgit with a long ē can mean he/she read (perfect)

In most modern printed Latin for beginners, vowel length may or may not be marked. Without macrons, the forms can look identical.

But in this sentence, the context makes present tense the right choice:

• sedet is present
• ludit is present
• dum suggests simultaneous action

So here legit clearly means reads / is reading.

Latin does not need to repeat the subject if it stays the same.

So:

• Pater in tablino sedet et epistulas legit

means:

• The father sits in the study and reads letters

Latin does not need to say pater ... et pater ... because once pater has been introduced, it is understood that he is the subject of both sedet and legit.

No, Latin word order is fairly flexible because the endings show the grammatical roles.

This sentence is arranged in a very natural and clear way:

• Pater first, as the main subject
• in tablino next, giving the place
• sedet et epistulas legit, the two actions
• dum filia in horto ludit, the while clause

A Latin author could rearrange many of these words without changing the basic meaning, though the emphasis might change. For example, epistulas pater legit would still mean the father reads letters.

The comma helps modern readers see the structure of the sentence:

• main clause: Pater in tablino sedet et epistulas legit
• subordinate clause: dum filia in horto ludit

In ancient Latin writing, punctuation was much less regular than in modern editions. So the comma is mainly an editorial aid, not something essential to the grammar itself.

Here are the nouns in the sentence:

• pater — from pater, patris: 3rd declension
• tablino — from tablinum, tablinī: 2nd declension neuter
• epistulas — from epistula, epistulae: 1st declension
• filia — from filia, filiae: 1st declension
• horto — from hortus, hortī: 2nd declension masculine

Knowing the declension helps you recognize the case endings:

• -as in epistulas = accusative plural
• -o in tablino and horto = ablative singular here
• -a in filia = nominative singular here