Post brevem quietem puer non iam sudat, sed lente spirat.

Because post is a preposition that takes the accusative case when it means after in a time expression like this.

So:

• post = after
• quietem = the accusative singular of quies (rest, quiet)
• brevem = accusative singular of brevis (short), agreeing with quietem

So post brevem quietem literally means after a short rest.

Because they are both in the accusative singular.

In Latin, adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here:

• quies is a feminine noun
• quietem is its accusative singular form
• brevis becomes brevem to match it

So the matching endings show that brevem describes quietem.

Because puer is the subject of the sentence: the boy is the one doing the actions.

Latin often marks the subject with the nominative case, and puer is nominative singular.

Compare:

• puer = the boy (subject)
• puerum = the boy (object)

In this sentence, the boy is not being acted on; he is the one who does not sweat and breathes slowly.

Non iam means no longer or not anymore.

It is made of:

• non = not
• iam = now / already

Together, in this kind of sentence, they mean that something used to be true but is true no more.

So:

• puer non iam sudat = the boy is no longer sweating

This is a very common Latin way to express no longer.

Yes, Latin can sometimes use both non iam and iam non, but the nuance and emphasis can vary depending on context and style.

For a beginner, the safest understanding here is:

• non iam = no longer

That is the natural meaning in this sentence.

Because the Latin present tense can cover both ideas:

• a simple present: he sweats / he breathes
• a progressive present: he is sweating / he is breathing

Latin does not have a completely separate form for is sweating the way English does.

So:

• sudat can mean he sweats or he is sweating
• spirat can mean he breathes or he is breathing

The context decides which English version sounds best.

The -t tells us the verb is third person singular in the present tense:

• sudat = he/she/it sweats or is sweating
• spirat = he/she/it breathes or is breathing

Since the subject is puer (the boy), we understand both verbs as he forms.

Because Latin has no articles.

English uses:

• the
• a/an

Latin does not. So a noun like puer can mean:

• the boy
• a boy

And brevem quietem can mean:

• a short rest
• the short rest

The context tells you which English article fits best.

Sed means but.

It contrasts the two parts of the sentence:

• non iam sudat = he is no longer sweating
• sed lente spirat = but he is breathing slowly

So sed marks a clear contrast: one action has stopped, and a different condition is now happening.

Lente is an adverb, meaning slowly.

It describes how the boy breathes:

• spirat = he breathes
• lente spirat = he breathes slowly

It comes from the adjective lentus, lenta, lentum, meaning slow or calm, but here the -e ending shows the adverb form.

Latin word order is more flexible than English word order because Latin uses case endings to show grammatical relationships.

English depends heavily on position:

• the boy sees the girl
• the girl sees the boy

Latin can move words around more freely because endings show who is subject and what belongs together.

In this sentence:

• Post brevem quietem comes first to set the time: after a short rest
• puer is the subject
• non iam sudat gives the first statement
• sed lente spirat gives the contrasting second statement

So the order is natural Latin, even if it feels less rigid than English.

Because Latin does not need to repeat the subject when it is already clear.

The sentence says:

• puer non iam sudat
• sed lente spirat

The -t ending on spirat already means he/she/it breathes, and the previous subject puer makes it clear that the boy is still the subject.

English often repeats the subject more explicitly, but Latin frequently leaves it understood.

It is a real and common enough Latin noun, but yes, its forms may look unusual to beginners.

Its dictionary form is quies, quietis and it means rest, quiet, repose.

In this sentence you see the accusative singular:

• nominative: quies
• accusative: quietem

So if quietem looks surprising, that is because the noun changes stem in its declined forms: quies / quiet-.

Yes. That is exactly how you usually want to translate it in natural English.

A very literal breakdown is:

• post = after
• brevem = short
• quietem = rest

But smooth English puts it together as:

• after a short rest

That is often the best way to understand Latin phrases: first see the grammar, then translate naturally.