Mater fenestram claudit, nē ventus frigidus in cubiculum intret.

Because fenestram is the direct object of claudit.

• fenestra = window as the basic dictionary form, nominative singular
• fenestram = window in the accusative singular

In this sentence, the mother is doing something to the window: she closes the window. Latin usually puts the direct object in the accusative case, so fenestra becomes fenestram.

Because mater belongs to a different declension. It is a third-declension noun, not a first-declension noun like fenestra.

Its nominative singular is simply mater, meaning mother. Here it is the subject of claudit, so it stays in the nominative case.

This is a good reminder that grammatical gender and noun ending do not always match in the way an English speaker might expect.

Nē introduces a negative purpose clause. In other words, it tells you what someone is trying to prevent.

So:

• ut = so that
• nē = so that ... not, lest

Here, Mater fenestram claudit, nē ventus frigidus in cubiculum intret means:

• The mother closes the window so that the cold wind does not enter the bedroom
• or more literally, ... lest the cold wind enter the bedroom

So nē is not just a simple word for not. It is specifically the normal way to introduce a negative purpose clause.

Because it is in a purpose clause introduced by nē.

Latin normally uses the subjunctive mood after ut or nē when expressing purpose:

• ut + subjunctive = so that
• nē + subjunctive = so that ... not / lest

So intret is the present subjunctive of intrat.

This is not saying that the wind actually enters. It expresses the mother's aim in closing the window: she closes it to prevent the wind from entering.

Intrat is the indicative form: he/she/it enters.

Intret is the present subjunctive: here it means something like may enter or would enter, depending on context.

Since this clause expresses purpose after nē, Latin requires the subjunctive, not the indicative.

So:

• intrat = a plain statement of fact
• intret = used here because the action is part of a purpose clause

Because in can take either the accusative or the ablative, depending on meaning.

• in + accusative = into, showing movement toward
• in + ablative = in / inside / on, showing location

Here the wind would move into the bedroom, so Latin uses the accusative:

• in cubiculum = into the bedroom

If the sentence were talking about location instead, it would use the ablative, for example:

• in cubiculō = in the bedroom

They are both nominative singular masculine.

That is because ventus is the subject of intret in the subordinate clause:

• ventus = wind
• frigidus = cold

The adjective frigidus agrees with ventus in case, number, and gender. Since ventus is masculine nominative singular, frigidus must be masculine nominative singular too.

So ventus frigidus means the cold wind.

Because Latin word order is much freer than English word order. Adjectives can come before or after nouns.

So both of these are possible:

• ventus frigidus
• frigidus ventus

Both mean cold wind.

Sometimes word order gives a different emphasis or style, but in a basic sentence like this, the main thing to notice is that frigidus agrees with ventus, no matter where it appears.

The comma helps separate the main clause from the subordinate purpose clause:

• main clause: Mater fenestram claudit
• purpose clause: nē ventus frigidus in cubiculum intret

In Latin manuscripts and ancient writing, punctuation was much less standardized than in modern editions. Modern textbooks usually add punctuation to make the structure easier to read.

So the comma is helpful, but it is not the core grammar. The real grammatical signal is nē + subjunctive.

Yes, very often.

Because Latin uses case endings to show grammatical relationships, word order is more flexible than in English. For example, these could still mean essentially the same thing:

• Mater fenestram claudit, nē ventus frigidus in cubiculum intret.
• Fenestram mater claudit, nē ventus frigidus in cubiculum intret.
• Nē ventus frigidus in cubiculum intret, mater fenestram claudit.

The endings tell you who is doing what:

• mater = subject of claudit
• fenestram = object of claudit
• ventus frigidus = subject of intret
• cubiculum = destination after in

Word order can still affect emphasis, but the basic grammar stays clear because of the endings.

Claudit is present indicative active, third person singular:

• she closes / is closing

Intret is present subjunctive active, third person singular:

• may enter
• or in smoother English here, enter

The present subjunctive is used because the purpose clause depends on a present main verb. This is part of the normal Latin sequence for purpose clauses.

Yes, that is a very literal way to understand it.

A more natural English translation is often:

• so that the cold wind does not enter the bedroom
• lest the cold wind enter the bedroom

The important thing is that the clause expresses prevention or intended avoidance, not just a plain negated fact.

So the mother is not merely stating the cold wind is not entering. She is closing the window to stop that from happening.