Fenestra aperta est, et ventus frigidus in cubiculum intrat.

Latin often uses a participle + est to describe a state.

• aperta = opened / open
• est = is

So fenestra aperta est literally looks like the window is opened, but in normal English it is often best understood as the window is open.

This is a very common Latin pattern. The participle behaves like an adjective and agrees with the noun it describes.

Because it agrees with fenestra.

Fenestra is:

• feminine
• singular
• nominative

So the word describing it must match those features:

• apertus = masculine
• aperta = feminine
• apertum = neuter

Since fenestra is feminine singular, Latin uses aperta.

Fenestra is nominative singular.

In this sentence it is the subject of est, so nominative is what you would expect. Also, first-declension nouns like fenestra commonly have -a in the nominative singular.

So:

• fenestra = the window as the subject

Formally, it can look like a passive construction, because it is built from a past participle plus est. But in a sentence like this, it is usually best understood as describing the window’s condition: the window is open.

So a learner should recognize two closely related ideas:

• grammatical form: participle + est
• practical meaning here: a state, not an action in progress

In other contexts, a similar form can mean something more like has been opened, but here the sense is simply that the window stands open.

Because frigidus is an adjective meaning cold, and it describes ventus.

Like aperta, it must agree with the noun:

• ventus is masculine singular nominative
• so the adjective is also masculine singular nominative: frigidus

Together:

• ventus frigidus = the cold wind

Because in takes different cases depending on meaning.

• in + accusative = motion into
• in + ablative = location in / inside

Here the wind is entering the room, so there is movement into it:

• in cubiculum = into the bedroom/room

If the sentence meant the wind is in the room, then you would expect in cubiculo.

Here cubiculum is accusative singular.

The preposition in requires the accusative when there is motion toward or into something. Since cubiculum is a neuter second-declension noun, its accusative singular ends in -um.

So:

• cubiculum = room / bedroom
• in cubiculum = into the room

Intrat is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from intrare, meaning to enter.

So ventus ... intrat means:

• the wind enters or more naturally,
• the wind is entering

Latin has no definite article like English the, and no indefinite article like a/an either.

So:

• fenestra can mean window or the window
• ventus frigidus can mean cold wind or the cold wind

You figure out which is best from context.

Because the verb ending already tells you the person and number.

For example:

• est = he/she/it is
• intrat = he/she/it enters

Since Latin verb endings carry that information, subject pronouns are often unnecessary unless the speaker wants emphasis or contrast.

Yes. Latin word order is much freer than English word order because the endings show how words function.

So this sentence could appear in other orders, for example:

• Aperta est fenestra, et ventus frigidus in cubiculum intrat.
• Ventus frigidus in cubiculum intrat, et fenestra aperta est.

The exact emphasis may shift, but the core meaning stays the same because the forms still show what belongs together.

Et simply means and.

It joins the two parts of the sentence:

• Fenestra aperta est
• ventus frigidus in cubiculum intrat

So it connects two statements:

• the window is open
• the cold wind enters the room

Usually, yes: cubiculum often means bedroom or sleeping room. In some contexts, though, it can be translated more generally as room or chamber.

So depending on the style of the translation, you might see:

• into the bedroom or
• into the room

Both are reasonable, but bedroom is often the more precise dictionary meaning.