Puer maestus domum redit.

Puer is in the nominative singular, which is the case normally used for the subject of a finite verb in Latin. So puer is the one doing the action of redit.

• puer = boy
• nominative singular ending here: no extra ending beyond the dictionary form

So the sentence is about the boy returning.

Maestus is an adjective modifying puer, so it must agree with it in:

• gender: masculine
• number: singular
• case: nominative

Since puer is masculine nominative singular, the adjective also appears in the masculine nominative singular form: maestus.

If the noun were feminine, you would expect maesta; if plural masculine, maesti, and so on.

By itself, maestus simply describes the boy as sad in the sentence. In context, it usually means he is sad at the time of the action.

So Puer maestus domum redit suggests the boy returns home sad or the sad boy returns home. Latin does not force a sharp distinction here.

Here domum is an example of the accusative of motion toward. With words for home and with names of cities and small islands, Latin often uses the accusative without a preposition to show movement toward a place.

So:

• domum = homeward / to home / home
• redit = returns

Together, domum redit means returns home.

Because Latin commonly omits a preposition with domus when it means home in expressions of motion.

English says to home only in special contexts, but normally just says home. Latin works similarly here:

• domum = home after a verb of motion
• not ad domum in this basic idiomatic expression

This is something you usually just learn as a standard Latin pattern:

• domum = homeward
• domi = at home
• domo = from home

Redit is:

• 3rd person singular
• present tense
• indicative mood
• active voice

It comes from redeo, redire, meaning to go back or to return.

So redit means he returns, she returns, or it returns. In this sentence, it refers to puer, so it means the boy returns.

Latin has no articles equivalent to English the or a/an.

So puer can mean:

• the boy
• a boy

Which one sounds best depends on the context and the translation choice. The Latin itself does not explicitly mark that distinction.

Yes. Latin word order is much more flexible than English word order because the endings show what each word is doing.

So all of these could express basically the same idea:

• Puer maestus domum redit.
• Maestus puer domum redit.
• Domum puer maestus redit.
• Puer domum redit maestus.

However, changing the order can slightly change emphasis or style. The original order is a very natural, straightforward one.

It is grammatically an adjective agreeing with puer, and in translation it can feel either:

• attributive: the sad boy returns home
• or somewhat predicative in sense: the boy returns home sad

Latin often allows this kind of overlap more easily than English. The adjective simply describes the subject while the action is happening.

Domus is the dictionary form, meaning house or home.
Domum is one of its inflected forms.

In this sentence, domum is the accusative singular, but it is being used in the special idiomatic sense homeward / home after a verb of motion.

So:

• domus = the base noun
• domum = a form of that noun, here meaning home

It is a second-declension masculine noun, but it is one of the type that keeps the -er in the nominative singular.

For example:

• puer = nominative singular
• pueri = genitive singular / nominative plural

So it belongs to the same declension as servus, but its nominative singular has a different shape. This is normal for some -er nouns in Latin.

In many contexts, domum with a verb of motion is best understood idiomatically as home rather than to the house.

That is why learners are usually taught to recognize:

• domum ire = to go home
• domum redire = to return home

If the writer wanted to focus on a specific building as a physical house, context would help make that clear. But in a simple sentence like this, home is the natural understanding.