Serva sarcinas trans atrium ad cubiculum portat.

Because serva is in the nominative singular, which is the form Latin commonly uses for the subject of the sentence.

• serva = female slave / maidservant as the one doing the action
• The action is portat = carries

So serva is the one who carries.

Serva is the feminine form, while servus is the masculine form.

• serva = a female slave / maidservant
• servus = a male slave / servant

So the sentence tells you that the person carrying the luggage is female.

Because sarcinas is in the accusative plural, which is the form Latin usually uses for a direct object.

The direct object is the thing being carried, so:

• serva = the subject, the one carrying
• sarcinas = the things being carried

The singular would be sarcina; the plural accusative is sarcinas.

The ending -as shows that it is accusative plural for a first-declension noun.

So sarcinas means bags / packs / pieces of luggage, not just one bag.

Compare:

• sarcina = one pack, bag, load
• sarcinas = several packs, bags, or loads

They show two different parts of the movement.

• trans atrium = across / through the atrium
• ad cubiculum = to / toward the bedroom

So the sentence is not just saying where she ends up. It also tells you the route she takes.

Because trans is a preposition meaning across or through, and it takes the accusative case.

So:

• trans
  • accusative
• atrium is accusative singular here

That is why you get trans atrium, not some other form.

Because ad means to or toward, and it also takes the accusative case.

So:

• ad
  • accusative
• cubiculum is accusative singular here

This shows motion toward the room.

Because both are second-declension neuter nouns, and in this sentence both are accusative singular.

For many second-declension neuter nouns:

• nominative singular ends in -um
• accusative singular also ends in -um

So here the form looks the same, even though the words are serving as objects of prepositions.

Related, yes, but in a Roman context it usually refers to the central hall of a Roman house.

So in this sentence, atrium is not just any modern open interior space. It means a specific part of a Roman home.

Cubiculum usually means bedroom or sleeping room.

In Roman-house vocabulary, it is a private room used especially for sleeping. So ad cubiculum means movement toward that room.

Latin word order is more flexible than English word order because Latin uses case endings to show each word’s job in the sentence.

A very common Latin pattern is to put the verb at the end, especially in straightforward narrative sentences.

So:

• Serva sarcinas trans atrium ad cubiculum portat.

is completely normal Latin word order.

The dictionary form is porto, meaning I carry, and the full verb is often listed as porto, portare.

Here:

• portat = he/she/it carries
• It is third person singular, present tense, active voice

Because the subject is serva, here it means she carries.

Latin often does not need a separate subject pronoun, because the verb ending already tells you the person and number.

• portat = he/she/it carries

Then the noun serva tells you who that she is. So Latin does not need to say ea portat unless it wants extra emphasis.

Classical Latin does not have articles like English the or a/an.

So a Latin noun like serva can mean:

• a slave / maidservant
• the slave / maidservant

Which one is meant depends on context. The same is true for atrium, cubiculum, and sarcinas.

Yes. Latin allows a lot of variation in word order, though some orders sound more natural than others.

For example, these could still mean roughly the same thing:

• Serva sarcinas ad cubiculum trans atrium portat.
• Sarcinas serva trans atrium ad cubiculum portat.

The endings still show the roles of the words. However, changing the order can slightly change the emphasis or what stands out most.

The verb form portat is present tense.

So it means:

• carries
• or in smoother English, sometimes is carrying, depending on context

Latin present tense can cover both a simple present and a present-in-progress idea, depending on the situation.