Pater ianuam firmius claudit, quia ventus frigidus est.

Because ianuam is the direct object of claudit: it is the thing the father is shutting.

• ianua = door
• ianuam = door in the accusative singular

Latin changes noun endings to show their job in the sentence. Since the father is acting on the door, ianua becomes ianuam.

Because pater is the subject of the sentence, not the object.

Here the father is the one doing the action:

• pater = the father as subject
• patrem = the father as direct object

So Latin keeps pater in the nominative case.

Firmius means more firmly or more tightly.

It is an adverb, modifying the verb claudit (shuts). It tells you how he shuts the door.

This form comes from the adjective firmus, -a, -um meaning firm or steady. Latin often forms adverbs like this:

• firmē = firmly
• firmius = more firmly

So the sentence suggests that the father is shutting the door more firmly than usual, probably because of the cold wind.

Because many Latin comparative adverbs have the same form as the neuter nominative/accusative singular of the comparative adjective.

So although firmius looks like an adjective form, here it is functioning as an adverb:

• firmior = firmer
• firmius = more firmly

This is normal in Latin. A learner often has to decide from context whether a form is being used adjectivally or adverbially. Here it clearly goes with claudit, so it is adverbial.

Because Latin word order is more flexible than English word order. The endings already show who is doing what, so Latin does not rely as heavily on position.

This sentence is arranged quite naturally:

• Pater = subject first
• ianuam = object next
• firmius = adverb before the verb
• claudit = verb at the end

Putting the verb at or near the end is very common in Latin, though not required. English depends much more on word order, while Latin depends more on inflection.

Yes, often it could. For example, Latin could also say:

• Pater firmius ianuam claudit
• Ianuam pater firmius claudit
• Quia ventus frigidus est, pater ianuam firmius claudit

These all keep basically the same core meaning because the endings still show the grammar.

However, changing the order can slightly change the emphasis:

• putting ianuam first may emphasize the door
• putting firmius earlier may emphasize how he shuts it
• putting quia ventus frigidus est first may emphasize the reason

Because quia simply introduces a clause meaning because and commonly takes a finite verb, here est.

So:

• quia = because
• ventus frigidus est = the wind is cold

This is a straightforward causal clause. For a beginner, the easiest way to understand it is just:

because the wind is cold

There are other ways Latin can express cause, but quia + normal verb is one of the most direct and common.

Because frigidus agrees with ventus, and ventus is masculine singular nominative.

• ventus = wind
• frigidus = cold, matching ventus

Adjectives in Latin must agree with the nouns they describe in:

• gender
• number
• case

Since ventus is masculine singular nominative, the adjective must also be masculine singular nominative: frigidus.

Because ventus is the subject of the verb est in the clause quia ventus frigidus est.

That clause literally means:

• ventus = the wind
• frigidus = cold
• est = is

So the wind is the thing being described as cold, which makes it the subject and therefore nominative.

Claudit is present tense, third person singular, from claudere meaning to shut or to close.

So it means:

• he shuts
• or sometimes he is shutting, depending on context

Latin present tense can often correspond to either simple present or progressive English. If the meaning shown to the learner is something like The father shuts the door more firmly, because the wind is cold, that is a perfectly normal translation.

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

So pater could mean:

• father
• the father
• sometimes even a father

You decide from context which English wording sounds best. In this sentence, the father is the most natural translation.

Not directly in form, but it belongs to the Latin verb claudere, which means to shut/close. English uses close, but Latin here uses its own common verb for shutting something.

A learner may also meet related Latin forms such as:

• claudo, claudere = shut, close
• clausus = closed, shut

So if you already know English words like closed or clause, the resemblance is not exact here, but the Latin root claud- / claus- is useful to remember.

Because Latin usually states the verb to be explicitly in sentences like this.

So:

• ventus frigidus est = the wind is cold

Latin can omit forms of esse in some special contexts, especially poetry, but in normal prose est is the standard and expected form here. It clearly completes the statement that the wind is cold.