Puella prudens rationem matris intellegit, sed frater stultus eandem rationem non intellegit.

They are in the nominative case, which is the case normally used for the subject in Latin.

• puella = the girl
• frater = the brother

You can tell they are the doers of the action because the sentence says that the girl understands, but the brother does not understand.

The verbs also help:

• intellegit = he/she understands

Since Latin often leaves subject pronouns unstated, the nouns in the nominative show who is doing the action.

Because rationem is the accusative singular form of ratio.

The accusative case is commonly used for the direct object, the thing being understood here.

So:

• ratio = nominative, reason / explanation / way of thinking
• rationem = accusative, reason / explanation / way of thinking as the object

In this sentence, both the girl and the brother are understanding or not understanding the reasoning, so Latin uses rationem.

Matris is genitive singular of mater, meaning of the mother.

So rationem matris means something like:

• the mother's reasoning
• the mother's point of view
• the mother's explanation

The genitive often shows possession or close connection, so matris tells us whose ratio it is.

Because prudens is a third-declension adjective with a different pattern from first-and-second-declension adjectives.

Its dictionary form is:

• prudens, prudentis = wise, sensible, prudent

For the nominative singular, both masculine and feminine use prudens. So:

• puella prudens = a sensible girl
• vir prudens = a sensible man

It does agree with puella, but agreement in Latin does not always mean the ending will look like the noun’s ending. It means the adjective matches in gender, number, and case.

Because stultus belongs to a different adjective pattern.

• stultus, -a, -um is a first-and-second-declension adjective
• prudens, prudentis is a third-declension adjective

So with a masculine noun like frater, Latin uses:

• frater stultus = the foolish brother

If the noun were feminine, it would be:

• puella stulta = the foolish girl

Different adjectives decline differently, even though they do the same basic job.

Eandem comes from idem, eadem, idem, meaning the same.

Here it is:

• feminine
• singular
• accusative

It has to match rationem, because it describes rationem.

So:

• eandem rationem = the same reasoning / the same explanation

This tells us that the brother fails to understand the very same reasoning that the girl understands.

Latin often avoids unnecessary repetition when the meaning is already clear.

The first half gives us rationem matris. Then the second half says eandem rationem, which means that same reasoning. The genitive matris does not need to be repeated because eandem points back to the earlier rationem.

So the sense is:

• the girl understands the mother's reasoning,
• but the foolish brother does not understand that same reasoning.

Because non usually negates the word or idea that follows, and very often it is placed directly before the verb.

So:

• non intellegit = does not understand

Latin word order is flexible, but non before the verb is extremely common and easy to recognize.

Latin relies much more on endings than on word order.

English usually depends heavily on order:

• The girl understands the mother's reasoning

Latin can move words around more freely because the endings show their roles:

• puella = subject
• rationem = direct object
• matris = genitive
• intellegit = verb

So Puella prudens rationem matris intellegit is natural Latin even though English would not normally place words in exactly that order.

Very often Latin puts the verb near the end, but that is a tendency, not an absolute rule.

No. Latin adjectives often stand near their nouns, but they do not have to.

In this sentence they do stand next to them:

• puella prudens
• frater stultus
• eandem rationem

But Latin can separate adjectives and nouns because agreement in gender, number, and case shows which words belong together.

So closeness helps, but the endings matter more.

Because Latin has no articles.

There is no separate word for the or a/an. Latin leaves that idea to be understood from context.

So:

• puella can mean girl, a girl, or the girl
• frater can mean brother, a brother, or the brother

When translating, English must choose an article, but Latin does not need one.

Yes, in some contexts Latin can omit a repeated verb if it is understood. But repeating it is completely normal and often clearer.

This sentence says:

• puella ... intellegit
• sed frater ... non intellegit

The repetition makes the contrast sharp and easy to follow:

• the girl understands,
• but the brother does not understand.

So the repeated verb is not redundant in a bad way; it is good, straightforward Latin.

Ratio is a very broad Latin word. Depending on context, it can mean:

• reason
• plan
• method
• account
• explanation
• way of thinking

In this sentence, rationem matris intellegit probably means something like:

• understands the mother's reasoning
• understands the mother's point of view
• understands the mother's explanation

So it is not just reason in the narrow logical sense; it can refer to the mother's thought process or argument.

Because both are feminine accusative singular.

• eandem = feminine accusative singular
• rationem = feminine accusative singular

In Latin, words that describe or modify a noun must agree with it in:

• gender
• number
• case

That is why eandem takes this form. If the noun were masculine or plural, the form would change.

Sed means but, and it sets up a contrast between the two parts of the sentence.

First half:

• Puella prudens rationem matris intellegit
• the sensible girl understands the mother's reasoning

Second half:

• sed frater stultus eandem rationem non intellegit
• but the foolish brother does not understand the same reasoning

The contrast works on two levels:

1. prudens vs. stultus
2. intellegit vs. non intellegit

So sed links two parallel ideas while emphasizing their difference.