Puer dicit matrem mox domum venturam esse.

Because after dicit (he says), Latin often uses an indirect statement rather than a clause with that.

In English, we say:

• The boy says that his mother will come home soon.

In Latin, that idea is commonly expressed as:

• Puer dicit matrem ... venturam esse.

In this construction:

• the subject of the reported statement goes into the accusative → matrem
• the verb of the reported statement goes into the infinitive → venturam esse

So matrem is not the direct object in the ordinary sense. It is the subject of the infinitive inside the indirect statement.

Because this is indirect speech / indirect statement after dicit.

Latin does not usually say the equivalent of The boy says that his mother will come with a normal future tense verb inside the subordinate clause. Instead, it uses:

• accusative + infinitive

So:

• matrem venturam esse = that his mother is going to come / will come

The infinitive here is specifically the future active infinitive, which is how Latin expresses a future action inside an indirect statement.

Venturam esse is the future active infinitive of venire (to come).

It is made from:

• the future active participle: venturus, ventura, venturum
• plus esse

Here the form is venturam esse because it agrees with matrem, which is:

• feminine
• singular
• accusative

So the pattern is:

• ventura
  • m → venturam
• then esse

Together: venturam esse = to be about to come / to be going to come / will come in indirect statement.

Because the participle must agree with matrem.

Mater, matris is a feminine noun. In this sentence, matrem is:

• feminine
• singular
• accusative

So the future participle must also be:

• feminine
• singular
• accusative

That gives venturam.

Comparison:

• venturus = masculine nominative singular
• ventura = feminine nominative singular
• venturum = masculine or neuter accusative singular
• venturam = feminine accusative singular

Because Latin often uses domum by itself to mean to home / homeward / home.

With many places, Latin uses a preposition such as ad with the accusative. But with home, the language has a special idiomatic usage:

• domum = home
• domi = at home
• domo = from home

So:

• domum venire = to come home

This is a very common expression and does not need ad.

Mox means soon. It modifies the idea of coming home, so it goes with venturam esse.

In other words:

• matrem mox domum venturam esse
• that mother will soon come home

Latin word order is flexible, so mox can often be moved around without changing the basic meaning very much. Here it naturally belongs with the future action.

Because Latin usually does not need a separate word corresponding to English that in this kind of sentence.

English says:

• The boy says that his mother will come home soon.

Latin says:

• Puer dicit matrem mox domum venturam esse.

The idea of that is built into the accusative-and-infinitive construction itself. So instead of a conjunction like that, Latin signals reported speech by changing the grammar of the clause.

The subject of the main sentence is puer (the boy).

So the structure is:

• puer = subject of dicit
• dicit = main verb
• matrem mox domum venturam esse = the indirect statement, functioning as what he says

Inside that indirect statement:

• matrem is the subject of venturam esse

So there are really two layers:

1. The boy says
2. his mother will come home soon

Latin expresses layer 2 with accusative + infinitive.

This feels strange to English speakers because English usually uses the nominative for a subject. But in Latin indirect statement, the subject is regularly put in the accusative.

So in this construction, the accusative noun is still the logical subject of the infinitive.

A useful way to read it is:

• Puer dicit = The boy says
• matrem = his mother (subject of the reported statement)
• venturam esse = will come / is going to come

So although matrem is accusative in form, it is still the one doing the coming.

It shows action that is future relative to the main verb dicit.

So the sentence means that, at the time the boy speaks, the mother’s coming is still in the future:

• He says [now] that his mother will come [later].

This is exactly why Latin uses the future infinitive here.

A helpful comparison:

• venire in indirect statement often suggests action happening at the same time as the main verb
• venisse suggests action earlier than the main verb
• venturam esse suggests action later than the main verb

Yes. Latin word order is much freer than English word order.

This sentence could be rearranged in various ways, for example:

• Puer matrem mox domum venturam esse dicit.
• Matrem puer mox domum venturam esse dicit.

The exact emphasis may shift slightly, but the grammar still shows the roles of the words:

• puer is nominative, so it is the main subject
• matrem is accusative, so it belongs to the indirect statement
• venturam esse is the future infinitive

So the meaning stays basically the same even if the order changes.

Latin often leaves possession implied when it is obvious from context.

Here, Puer dicit matrem ... will naturally be understood as The boy says that his mother ..., unless the context suggests someone else’s mother.

If Latin wanted to be more explicit, it could say matrem suam. But very often the possessive is omitted when it is clear enough without it.

So:

• matrem can naturally mean his mother
• matrem suam would be more explicit: his own mother

Yes, literally that is close to how it works.

The future participle often has the sense about to or going to, and with esse it forms the future infinitive. So literally:

• venturam esse = to be about to come

But in normal translation of indirect statement, it is usually best rendered more naturally as:

• will come
• is going to come

So the literal sense helps you understand the grammar, but the natural English translation is usually smoother.