Mater promittit se vicinas quoque invitaturam esse.

The sentence has:

• a main clause: Mater promittit = Mother promises
• an indirect statement (also called an accusative-and-infinitive construction): se vicinas quoque invitaturam esse

So literally the structure is:

• Mother promises
• herself to be going to invite the neighbors too

More natural English is:

• Mother promises that she will invite the neighbors too
• or simply Mother promises to invite the neighbors too

Latin often uses this accusative + infinitive pattern where English would use that plus a finite verb.

Se is the reflexive pronoun, meaning herself / himself / themselves, depending on context.

Here it refers back to the subject of the main verb, Mater. So:

• Mater promittit = Mother promises
• se ... invitaturam esse = that she will invite ...

Latin uses se because the person doing the promising is also the person who will do the inviting.

If Latin used eam instead, that would normally mean her as someone else, not the mother herself.

So:

• se = she herself, referring back to Mater
• eam = her, referring to some other female person

Because in a Latin indirect statement, the subject of the subordinate idea goes into the accusative, and the verb goes into the infinitive.

So instead of something like:

• ea invitabit = she will invite

Latin turns that into an indirect statement after promittit:

• se invitaturam esse = that she will invite

This is a very common Latin pattern:

• dicit se venire = he says that he is coming
• putat eum sapere = she thinks that he is wise
• promittit se facturam esse = she promises that she will do it

So se is accusative because it is the subject of the infinitive phrase.

Invitaturam esse is the future active infinitive of invitare.

It means:

• to be going to invite
• to be about to invite
• in smoother English here: will invite

It is formed from:

• the future active participle: invitatura = about to invite (feminine singular nominative form)
• plus esse = to be

In this sentence the form is invitaturam esse, not invitatura esse, because it has to agree with se in the accusative feminine singular.

So:

• se invitaturam esse = that she will invite

This future infinitive is used because the inviting happens after the promising.

Because it agrees with se, which refers to Mater.

The future active participle must match its subject in:

• gender
• number
• case

Here the subject of the infinitive is se, referring to Mother, so the participle must be:

• feminine: because Mother is female
• singular: because it is one person
• accusative: because the subject of an indirect statement is accusative

So the form is:

• invitaturam

If the subject were masculine singular, it would be invitaturum. If it were plural feminine, it would be invitaturas, and so on.

Because invitare is a present infinitive, while invitaturam esse is a future infinitive.

That difference matters.

• invitare would suggest action that is simultaneous with the main verb, or at least not clearly future relative to it
• invitaturam esse clearly shows that the inviting will happen later, after the promise

Since a promise is about a future action, Latin naturally uses the future infinitive here.

So the sentence means not just Mother promises that she invites, but Mother promises that she will invite.

Vicinas is the accusative plural feminine form of vicina, meaning neighboring woman or female neighbor.

Here it is the direct object of invitare:

• invite whom? → vicinas

So it must be in the accusative.

Because the form is feminine plural, it specifically means female neighbors or the neighboring women.

A native English speaker may not expect this, because English neighbors does not usually show gender. But Latin does.

Compare:

• vicinos = male neighbors / neighbors in a masculine or mixed group
• vicinas = female neighbors

Quoque means also or too, and it usually comes after the word it emphasizes.

So:

• vicinas quoque = the neighbors too / the female neighbors also

This suggests that the mother will invite the neighbors in addition to someone else already understood from the context.

This is different from etiam, which often comes before the word or phrase it emphasizes.

A useful rule of thumb:

• quoque = often after
• etiam = often before

So the placement of quoque here is normal Latin.

Because Latin usually does not use a conjunction equivalent to English that in this kind of sentence.

English says:

• Mother promises that she will invite the neighbors too

Latin instead uses the accusative-and-infinitive construction:

• Mater promittit se vicinas quoque invitaturam esse

So the idea of English that is built into the grammar of se ... invitaturam esse rather than expressed by a separate word.

No. That is a very common point of confusion.

In this sentence, se is not the thing being promised. It is the subject of the infinitive inside the indirect statement.

So the structure is not:

• Mother promises herself

It is:

• Mother promises [that she will invite the neighbors too]

Inside that bracketed part:

• se = the subject
• vicinas = the direct object
• invitaturam esse = the infinitive verb phrase

So se belongs with invitaturam esse, not directly with promittit.

Latin word order is fairly flexible, because the endings show the grammatical roles.

So this sentence could be rearranged in various ways without changing the core meaning, for example:

• Mater se vicinas quoque invitaturam esse promittit
• Mater vicinas quoque se invitaturam esse promittit

The actual order used can affect emphasis and style, but not the basic grammar.

The given order is perfectly normal:

• Mater promittit first gives the main statement
• then se vicinas quoque invitaturam esse explains what is promised

Yes. In natural English, that is often the best translation.

Latin says more literally:

• Mother promises that she will invite the neighbors too

But English commonly shortens this to:

• Mother promises to invite the neighbors too

Both translations are acceptable, as long as you understand the Latin grammar underneath:

• se shows that the person who promises is also the person who will do the inviting
• invitaturam esse shows that the action is future relative to promittit