Post longam horam requies brevis discipulis valde bona est.

Because post is a preposition that takes the accusative case when it means after.

So:

• post = after
• horam = hour in the accusative singular
• longam matches horam in case, number, and gender, so it also becomes accusative singular

That is why Latin uses post longam horam for after a long hour.

Because the phrase is the object of the preposition post, and post requires the accusative.

Compare:

• longa hora = a long hour, as a subject or in some other nominative use
• longam horam = a long hour, in the accusative after post

English does not show this change very much, but Latin does.

The subject is requies brevis.

You can tell because:

• requies is nominative singular
• brevis agrees with it in nominative singular feminine
• the verb est is singular, matching that subject

So the sentence is about a short rest.

Because here the phrase is the subject, not a direct object.

Latin uses the nominative for the subject:

• requies = rest, in the nominative
• brevis = short, agreeing with requies

If it were a direct object, then you would expect accusative forms such as requiem brevem.

Because brevis belongs to a different adjective pattern.

Latin adjectives are not all declined the same way:

• longus, longa, longum and bonus, bona, bonum are first/second-declension adjectives
• brevis, breve is a third-declension adjective

So even though longam, brevis, and bona are all adjectives, they do not all have the same endings.

Here:

• brevis is nominative singular feminine, agreeing with requies
• it does not need to look like bona, because it comes from a different declension pattern

Because it describes requies, which is a feminine singular noun.

Latin adjectives must agree with the noun they describe in:

• gender
• number
• case

So:

• requies = feminine singular nominative
• bona = feminine singular nominative

That is why Latin says bona est, not bonum est or bonus est.

Discipulis is in the dative plural and means for the students.

This is a very common Latin use of the dative: the dative of advantage or reference.

So the sentence is not saying that the students are the subject. Instead, it means that the short rest is good for them.

• discipuli = the students
• discipulis = to/for the students

Because Latin often expresses ideas like for someone just by using the dative case.

English usually needs a separate word such as for, but Latin can often do the same job with an ending.

So:

• English: good for the students
• Latin: discipulis bona

The ending -is in discipulis shows its function.

Valde modifies bona.

It means very, so:

• bona est = is good
• valde bona est = is very good

In other words, valde strengthens the adjective bona.

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

Latin often puts the verb at or near the end, especially in straightforward prose. That does not change the basic meaning.

So:

• requies brevis discipulis valde bona est
• and some other word orders

can mean the same thing, as long as the endings make the grammar clear.

The chosen order here gives a natural flow:

• first the time phrase: post longam horam
• then the subject: requies brevis
• then who it concerns: discipulis
• then the description: valde bona
• finally the verb: est

Yes, often they could.

Because Latin relies heavily on case endings, the sentence can usually survive some rearrangement without changing its core meaning.

For example, these would still be understandable Latin:

• Requies brevis post longam horam discipulis valde bona est.
• Discipulis post longam horam requies brevis valde bona est.

However, word order still matters for emphasis and style. The original sentence puts post longam horam first, which emphasizes the idea of after a long hour.

It is a third-declension noun, and yes, it may look less familiar at first if you have mostly seen first- and second-declension nouns.

Its dictionary form is requies, requietis, feminine, meaning rest.

That helps explain why:

• the nominative singular is requies
• the adjective agreeing with it is feminine: brevis, bona

So the form is perfectly normal, just from a different declension pattern than nouns like puella or servus.

Because they do two different jobs.

• brevis directly describes the noun requies: a short rest
• bona works with est to say something about the subject: is good

So the structure is:

• requies brevis = the short rest
• discipulis valde bona est = is very good for the students

This is similar to English in:

• The short rest is very good for the students.

Here short is attached directly to rest, while good comes after is.

The verb est tells you that.

In requies brevis discipulis valde bona est, bona is linked to the subject by est, so it is a predicate adjective: it tells you what the subject is.

If both adjectives were simply attached to the noun, the structure would feel different. Here the meaning is clearly:

• the short rest = subject
• is very good = statement about the subject

So brevis is attributive, while bona is predicative.

A helpful breakdown is:

• Post longam horam = after a long hour
• requies brevis = a short rest
• discipulis = for the students
• valde bona est = is very good

So the grammar works like this:

• time phrase
• subject
• dative phrase
• predicate with verb

This is a good way to read Latin: identify the prepositional phrase, subject, indirect/dative phrase, and main verb.