Pater dicit se post cenam longum sermonem cum familia habiturum esse.

Because se is the reflexive pronoun. It refers back to the subject of the main verb, which is pater.

So:

• Pater dicit se ... habiturum esse = Father says that he ... will have
• Here he means the father himself

If Latin used eum instead, it would usually mean some other male person, not the subject pater.

This is the Latin indirect statement construction, often called the accusative and infinitive construction.

After a verb like dicit (says), Latin often does not use a word like that. Instead, it uses:

• an accusative subject → se
• an infinitive → esse
• and any other words that go with that infinitive → post cenam longum sermonem cum familia habiturum

So the structure is:

• Pater dicit = father says
• se ... habiturum esse = that he will have ...

Because the sentence is talking about an action that is future relative to dicit.

• habere = to have
• habiturum esse = to be going to have / to be about to have / will have

In indirect statement, Latin uses the future active infinitive to show future time.

So:

• se habere = that he has / is having
• se habiturum esse = that he will have

It is the future active infinitive of habeo.

It is built from:

1. the future active participle: habiturus, -a, -um
2. plus esse

Here we get habiturum esse because it agrees with se, which is:

• masculine
• singular
• accusative

Since se refers to pater, the form must be masculine singular accusative: habiturum.

Because it agrees with se, the subject of the infinitive.

In an indirect statement, the subject is put into the accusative case. Since se is accusative, the participle agreeing with it must also be accusative.

So:

• se = accusative singular
• habiturum = accusative singular masculine

They belong together: se habiturum esse = that he will have

Because post is a preposition that takes the accusative case.

So:

• cena = dinner, meal
• cenam = accusative singular
• post cenam = after dinner

This is just normal preposition usage in Latin.

Because it is the direct object of habiturum esse.

The verb habere takes a direct object:

• sermonem habere = to have a conversation / discussion

And longum agrees with sermonem:

• sermonem = accusative singular masculine
• longum = accusative singular masculine

So longum sermonem means a long conversation.

Not exactly in the modern English sense of a formal speech.

In Latin, sermo often means:

• conversation
• talk
• discussion

So longum sermonem habere cum familia is more naturally understood as:

• to have a long conversation with the family
• to talk for a long time with the family

It is less likely to mean a formal speech delivered to them.

Yes, literally it is to have a conversation, and that is a normal Latin idiom.

English also says have a conversation, so in this case the idiom is actually quite similar in both languages.

So:

• sermonem habere = to have a conversation / talk

This is a very natural expression in Latin.

Because cum means with, and cum takes the ablative case.

So:

• familia is ablative singular
• cum familia = with the family

That is the regular construction.

Not always.

In Latin, familia can mean:

• a household
• family members
• even the whole household, including servants/slaves, depending on context

In a sentence like this, a learner will usually understand it as family or household. The exact nuance depends on context.

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

English says:

• Father says that he will have a long conversation...

Latin normally says:

• Pater dicit se ... habiturum esse

So the idea of that is built into the accusative + infinitive construction, not expressed by a separate word.

The conversation is future, not the saying.

• dicit = he says / is saying → present
• habiturum esse = that he will have → future relative to dicit

So the meaning is:

• Father says now that later, after dinner, he will have a long conversation with the family.

It goes most naturally with habiturum esse.

That means:

• he says now
• that after dinner he will have a long conversation

So post cenam tells us when the future conversation will happen, not when he says it.

Yes. Latin word order is much freer than English word order because the grammatical relationships are shown by endings.

For example, the following would still mean essentially the same thing:

• Pater se cum familia post cenam longum sermonem habiturum esse dicit.
• Se post cenam cum familia longum sermonem habiturum esse pater dicit.

However, the original order is perfectly natural and clear.

In this sentence, the normal interpretation is no: it refers back to pater.

That is what reflexive se normally does in indirect statement after a verb like dicit.

So:

• Pater dicit se ... = Father says that he himself ...

If Latin wanted to make it clear that another man was meant, it would usually use a non-reflexive form such as eum.

Yes, it could be changed, but the meaning would change slightly.

• dicit = he says / is saying
• dixit = he said / has said

The indirect statement would stay the same in structure, but the time reference would shift depending on context.

For example:

• Pater dicit se ... habiturum esse = Father says that he will have ...
• Pater dixit se ... habiturum esse = Father said that he would have ...

So the tense of dicit affects the frame of the whole sentence.

The main finite verb is dicit.

Everything from se to esse is part of the indirect statement depending on dicit.

So the sentence breaks down like this:

• Main clause: Pater dicit
• Indirect statement: se post cenam longum sermonem cum familia habiturum esse

That is a very useful way to analyze Latin sentences of this kind.