Servi aedes nocte custodiunt.

Because servi is nominative plural, the form you expect for the slaves / the servants as the subject of the sentence.

It also matches the verb custodiunt, which is third person plural: they guard.

So:

• servi = the slaves as subject
• custodiunt = they guard

Those two naturally go together.

Here aedes is the direct object, so it is in the accusative.

The verb custodiunt means guard and takes a direct object: you guard something.

So in this sentence:

• servi = subject
• aedes = object
• custodiunt = verb

A tricky point is that aedes is a form that can look ambiguous, because this noun has some forms that are spelled the same in different cases and numbers. In this sentence, the syntax shows that aedes is the thing being guarded.

This is one of the confusing things about the word.

Aedes can be tricky because:

• it can appear as a singular form in some uses
• it can also appear as a plural form
• and in some contexts it is often translated as a singular English word such as house

So a learner often has to rely on context and vocabulary information.

In this sentence, the exact English translation you were given will tell you whether it is being understood as house, building, or buildings. The important grammar point here is that it is the object of custodiunt.

Because Latin often uses the ablative case to express time when, without a preposition.

So nocte is an ablative form meaning:

• at night
• by night

This is a very common Latin pattern. English usually needs a preposition like at, but Latin often does not.

It is an ablative of time when.

That means it tells you when the action happens:

• nocte = at night
• compare other time expressions like prima luce = at first light

So nocte answers the question when do they guard?

Custodiunt is:

• present tense
• active voice
• indicative mood
• third person plural

So it means they guard or they are guarding, depending on context.

It comes from the verb custodire, meaning to guard, to watch, or to protect.

Because that is very common in Latin.

Latin word order is much more flexible than English word order because the endings show the grammatical function of the words. A Latin sentence often places the verb at or near the end.

So:

• Servi aedes nocte custodiunt
• literally something like The slaves the house at night guard

That sounds strange in English, but it is perfectly normal in Latin.

Yes, often they could.

For example, Latin could also say things like:

• Nocte servi aedes custodiunt
• Aedes servi nocte custodiunt
• Custodiunt servi aedes nocte

The basic meaning would stay similar because the endings help show who is doing what.

However, different word orders can create different emphasis. For example:

• putting nocte earlier might emphasize when
• putting aedes earlier might emphasize what is being guarded

Because Latin does not have articles like English the and a/an.

So a Latin noun like servi can mean:

• slaves
• the slaves

And aedes can mean:

• a house / a building
• the house / the building
• or a plural meaning, depending on context

You decide from context and from the translation being used.

It can mean either, depending on context.

The Latin present tense often covers both:

• they guard
• they are guarding

It can also sometimes describe a habitual action:

• they guard at night
• they guard the house at night

So the best English translation depends on the wider context.

Most basically, servus means slave, and servi is the plural.

In some learning materials or some contexts, it may be translated more loosely as servants, but slave is usually the more direct historical meaning.

So if your textbook gives servants, that may be for smoother English, but the Latin word itself normally refers to enslaved people.

Because it is a direct object, and direct objects in Latin normally do not need a preposition.

The verb custodire is transitive: you guard something.

So Latin simply says:

• servi aedes custodiunt = the slaves guard the house/building

No extra word like to or at is needed before the object.