Lucia sententiam iterum emendat et matri rescribit se cras ad scholam venturam esse.

Because it is the direct object of emendat.

• emendat = she corrects / revises
• What does she correct? sententiam

So sententia becomes sententiam because direct objects normally go in the accusative in Latin.

Iterum means again.

It is an adverb, so it modifies the verb emendat: Lucia corrects the sentence again.

Its position is normal. Latin word order is flexible, and adverbs are often placed near the word they modify. Here iterum right before emendat makes good sense.

Because matri is dative singular, and it is the indirect object of rescribit.

• mater = mother as a subject
• matri = to her mother

So:

• Lucia matri rescribit = Lucia writes back to her mother

The person receiving the letter/message is commonly put in the dative.

Rescribit means writes back, replies in writing, or simply responds by letter/message.

It is from rescribo:

• scribo = I write
• rescribo = I write back / reply

So the sentence is not just saying Lucia writes something; it says she is replying to her mother.

Because after verbs of saying, thinking, knowing, writing, and similar verbs, Latin often uses an indirect statement construction rather than a that-clause.

The pattern is:

• accusative subject + infinitive

Here:

• se = the subject of the indirect statement
• venturam esse = to be going to come / will come

So matri rescribit se cras ad scholam venturam esse literally means:

• she writes back to her mother herself to be going to come to school tomorrow

Natural English:

• she writes back to her mother that she will come to school tomorrow

Because se is the reflexive pronoun, and it refers back to the subject of the main verb, which is Lucia.

So:

• Lucia ... rescribit se ... venturam esse = Lucia writes back that she herself will come

If Latin used eam, that would normally mean her in the sense of some other female person, not Lucia herself.

This is a very important distinction:

• se = refers back to the subject (Lucia)
• eam = refers to another female person

Venturam is the future active participle of venio (to come).

Its dictionary pattern is:

• venio, venire, veni, ventum

The future participle is built from vent- plus adjective endings:

• venturus = masculine singular
• ventura = feminine singular
• venturum = neuter singular

Here it appears as venturam because it agrees with se, which refers to Lucia, a feminine singular subject in the accusative.

So:

• se ... venturam esse = that she will come

More literally:

• herself to be about to come

Because venire is the present infinitive, meaning to come, while venturam esse is the future infinitive, meaning to be going to come / will come.

Latin needs the future infinitive here because the action is future relative to rescribit.

Compare:

• se venire = that she is coming / comes
• se venturam esse = that she will come

Since the sentence includes cras (tomorrow), the future form is exactly what we expect.

Because the future meaning comes from the combination future participle + esse, which is how Latin forms the future infinitive.

So:

• venturam esse is a single verbal idea meaning to be going to come / will come

The infinitive is not future because esse itself is future; it is future because venturam is a future participle.

Because ad with the accusative often expresses motion toward a place.

• schola = school
• ad scholam = to school

Since Lucia will come to school, the phrase of motion is appropriate.

A learner might wonder why Latin does not simply use the accusative without a preposition, but school is not one of the small group of words like domum where Latin often omits the preposition for motion toward.

It belongs in sense to the indirect statement.

Lucia is not writing back tomorrow; she is writing back that she will come tomorrow.

So the meaning is:

• Lucia writes back to her mother [that she will come to school tomorrow].

Latin does not need any extra marker to show this; the context and structure make it clear.

There are two clues.

1. The pronoun

• se normally refers back to the subject of the main clause, which is Lucia

2. The grammar

• venturam agrees with se, not with matri
• matri is dative (to her mother), while the subject of the indirect statement must be accusative, here se

So the sentence means Lucia says she herself will come, not that her mother will come.

Both are present active indicative, third person singular.

• emendat = she corrects / is correcting
• rescribit = she writes back / is writing back

In English, either a simple present or a progressive translation may fit depending on context. Latin present tense can cover both ideas.

It has two main verbs joined by et:

• Lucia sententiam iterum emendat
• et matri rescribit se cras ad scholam venturam esse

So the structure is:

• Lucia = subject
• sententiam = direct object of emendat
• iterum = adverb
• emendat = first main verb
• et = and
• matri = indirect object of rescribit
• rescribit = second main verb
• se cras ad scholam venturam esse = indirect statement depending on rescribit

In other words:

1. Lucia corrects the sentence again.
2. She writes back to her mother that she will come to school tomorrow.