Pater idem dicit quod mater dicit.

Yes. Here idem means the same thing.

A very common first reaction is to assume it describes pater, as if it meant the same father, but that is not what is happening here. In this sentence, idem is the direct object of dicit, so it means the same thing.

So the structure is:

• Pater = the father
• idem = the same thing
• dicit = says

So: Father says the same thing ...

Because the form idem can represent more than one grammatical possibility.

Here it is best understood as neuter singular accusative, meaning the same thing. That is the form Latin uses because it is the object of dicit.

It just happens that idem is also the form for masculine nominative singular. So the form looks ambiguous by itself, but the sentence makes the function clear.

In other words:

• pater is the subject
• idem is the object

So idem does not agree with pater here.

Here quod introduces a relative clause and means something like:

• which
• that which
• what

So quod mater dicit means what the mother says or that which the mother says.

The whole sentence is built like this:

• Pater idem dicit = Father says the same thing
• quod mater dicit = that the mother says / what the mother says

Together: Father says the same thing that the mother says.

Because it is the object of the second dicit.

Inside the clause quod mater dicit, the mother is the subject, and quod is the thing being said. So grammatically it works like:

• mater = subject
• dicit = says
• quod = object

That is why quod is accusative.

This is an important point: the case of a relative pronoun is determined by its role inside its own clause, not just by the word it refers back to.

No. That is a very common confusion.

Latin quod can sometimes mean because, but here it is clearly a relative pronoun, not a conjunction of cause.

Why?

Because in this sentence it refers to idem and functions as the object of dicit in the clause quod mater dicit.

So here it means what or that which, not because.

Because there are really two clauses, and each clause has its own verb:

1. Pater idem dicit
2. quod mater dicit

English sometimes avoids repetition more freely, but Latin often states the verb again when each clause needs its own finite verb.

So the repetition is normal and clear:

• the father says
• the mother says

Because Latin has no articles.

Latin does not have separate words for the or a/an. So:

• pater can mean father, the father, or sometimes a father
• mater can mean mother, the mother, or sometimes a mother

The context tells you which English wording is most natural.

They are both in the nominative singular because each is the subject of its own verb.

• Pater dicit = Father says
• Mater dicit = Mother says

So both nouns are doing the action of saying, which is why they are nominative.

Latin word order is more flexible than English word order because Latin uses endings to show grammatical roles.

So this sentence could be rearranged in other ways and still mean essentially the same thing, as long as the forms stay the same.

For example, Latin often allows emphasis through word order. But the given order is very straightforward:

• Pater idem dicit first
• then quod mater dicit

That makes it easy to understand as: Father says the same thing that mother says.

Not for this exact meaning.

Latin often uses an accusative-and-infinitive construction after verbs of saying, thinking, knowing, and so on. But that construction is used for reported statements, like he says that X is happening.

Here, though, the sentence is not simply reporting a statement. It is comparing what one person says with what another person says:

• Father says the same thing
• as / that mother says

So the relative clause with quod is the natural way to express that idea.

Yes, more or less.

A very literal breakdown would be:

• Pater = Father
• idem = the same thing
• dicit = says
• quod = what / that which
• mater = mother
• dicit = says

So literally: Father says the same thing which mother says.

In smoother English, we usually say: Father says the same thing that mother says.