Illa nox, quae initio plena pavoris fuit, postea serena et quieta facta est.

Illa is nominative feminine singular. It agrees with nox, which is also nominative feminine singular.

Here it means that night, or sometimes that particular night. Latin often uses demonstratives like ille, illa, illud where English might simply say the or might leave the emphasis unstated.

So illa nox = that night.

Nox is a feminine noun in Latin, meaning night. Its dictionary form is nox, noctis.

In this sentence, nox is in the nominative singular, because it is the subject of both:

• fuit = was
• facta est = became / was made

Everything describing the night must match it in gender and number.

Quae here means which.

It is a relative pronoun introducing the clause:

quae initio plena pavoris fuit
= which at first was full of fear

It is feminine singular because it refers back to nox.

It is nominative because it is the subject of fuit inside the relative clause.

A useful rule:

• a relative pronoun agrees with its antecedent in gender and number
• but its case depends on its job inside its own clause

So:

• antecedent: nox → feminine singular
• role in relative clause: subject of fuit → nominative

Initio is the ablative singular of initium.

Here it is used in an adverbial sense meaning:

• at first
• at the beginning
• initially

So:

quae initio plena pavoris fuit
= which at first was full of fear

This is a very common Latin usage. English often uses an adverb like initially, while Latin can use an ablative noun phrase.

Because plena is the adjective full, and Latin usually expresses full of something with the genitive.

So:

• plena = full
• pavoris = of fear (genitive singular of pavor)

Together: plena pavoris = full of fear

This is a common pattern with plenus, -a, -um.

Pavoris is the genitive singular of pavor, which means fear, panic, or dread.

Its job is to depend on plena:

• plena pavoris = full of fear

A learner may notice that English uses of here, and Latin often uses the genitive where English uses of.

Fuit is the perfect tense of sum and here means was in the sense of a completed past fact.

Erat is the imperfect tense, which often gives background description or an ongoing past state.

So the difference is roughly:

• fuit = was / turned out to have been / a completed past state viewed as a whole
• erat = was being / used to be / background or ongoing description

In this sentence, the writer is narrating the night as a completed event:

• at first it was full of fear
• later it became calm and quiet

That makes the perfect tense natural.

Yes, facta est literally looks like was made, but in this kind of sentence it often means became.

So:

serena et quieta facta est
= became serene and quiet

This expresses a change of state:

• earlier: full of fear
• later: calm and quiet

Grammatically:

• facta is the perfect passive participle of facio
• est is a form of sum

But in idiomatic English, became is usually the best translation here.

Because they are adjectives describing nox.

Since nox is feminine singular nominative, the adjectives must also be:

• feminine
• singular
• nominative

So:

• serena = serene, calm
• quieta = quiet, peaceful

These are called predicate adjectives, because they describe the subject after the verb:

• the night became calm and quiet

Postea is an adverb meaning:

• afterward
• later
• after that

It marks the shift from the earlier state to the later one:

• initio = at first
• postea = later

So the sentence has a clear time contrast:

• at first, the night was full of fear
• later, it became serene and quiet

Because Latin word order is much more flexible than English word order.

The main statement is:

Illa nox ... postea serena et quieta facta est.
= That night ... later became serene and quiet.

The relative clause is inserted after nox:

quae initio plena pavoris fuit
= which at first was full of fear

Latin often places descriptive material right after the noun it describes. English does this too with which, but Latin allows even more flexibility.

A good way to break it down is:

• Illa nox = subject, that night
• quae initio plena pavoris fuit = relative clause describing the night
• postea serena et quieta facta est = main predicate, later became serene and quiet

So the skeleton is:

Illa nox ... facta est.
= That night ... became ...

And inside it is the inserted description:

quae ... fuit
= which ... was

This is a very common Latin sentence pattern:

• noun
• relative clause
• rest of main clause

Yes. Latin allows several word orders without changing the basic meaning, because the endings show the grammatical relationships.

For example, the author could rearrange parts for emphasis. But the given order is elegant and clear:

• Illa nox sets up the subject
• the relative clause explains its earlier condition
• postea introduces the contrast
• facta est comes at the end, where Latin often places the verb

So the order is not random; it helps the sentence unfold neatly from:

1. the night
2. what it was like at first
3. what it later became