Nemo respondet, quia serva in horto aquam portat.

Because nemo means no one or nobody, and in Latin it is grammatically singular. Since the subject is singular, the verb must also be singular.

• nemo = singular subject
• respondet = he/she/it responds, 3rd person singular present

So Latin treats no one as one person: nobody rather than a plural group.

Yes. Latin often uses a single word where English uses two.

• nemo = no one / nobody

It is a very common word and already includes the negative idea, so Latin does not need an extra word like non here.

So:

• nemo respondet = no one responds
• not nemo non respondet

Quia means because. It introduces a clause that gives the reason for what was just said.

So the structure is:

• main clause: Nemo respondet
• reason clause: quia serva in horto aquam portat

In other words, quia connects the two ideas and shows that the second clause explains the first.

Because serva is the subject of portat, and subjects are put in the nominative case.

Here:

• serva = nominative singular
• it means the female slave / maidservant
• she is the one doing the carrying

So serva is nominative because she is the one performing the action.

Because aquam is the direct object of portat. It is the thing being carried, so it must be in the accusative case.

• aqua = nominative singular
• aquam = accusative singular

Since the slave is carrying water, Latin marks water as the object with the accusative ending -m.

Because in can take different cases depending on the meaning:

• in + ablative = in / on a place, showing location
• in + accusative = into / onto a place, showing motion toward

Here the meaning is location: the slave is carrying water in the garden, not into the garden.

So:

• in horto = in the garden
• in hortum would mean into the garden

In Latin, case endings usually tell you this more clearly than word order does.

In this sentence:

• serva has the nominative ending, so it is the subject
• aquam has the accusative ending, so it is the direct object

That means:

• serva is doing the carrying
• aquam is what is being carried

Even if the word order changed, the endings would still help you identify the roles.

Yes. Latin word order is more flexible than English word order because Latin uses endings to show grammatical function.

For example, these would mean the same basic thing:

• serva in horto aquam portat
• aquam serva in horto portat
• in horto serva aquam portat

The exact order can change emphasis or style, but the case endings still show who is subject and who is object.

Yes. Both are present tense, 3rd person singular, active voice.

• respondet = he/she/it responds
• portat = he/she/it carries

Because the subjects are singular:

• nemo → respondet
• serva → portat

So both actions are being described as happening in the present.

Classical Latin has no articles. It does not have separate words for the, a, or an.

So:

• serva can mean a slave, the slave, or sometimes just slave, depending on context
• horto can mean in a garden or in the garden
• aquam can mean water or the water, depending on context

English has to choose an article, but Latin usually leaves that to context.

Serva is a first-declension feminine noun.

Its basic dictionary form is:

• serva, servae = female slave, maidservant

Some useful forms are:

• serva = nominative singular
• servae = genitive singular / nominative plural
• servam = accusative singular
• servā = ablative singular

In this sentence, the nominative singular serva is used because she is the subject of portat.

It comes from hortus, horti, a second-declension masculine noun meaning garden.

Here the form is horto, which is ablative singular. It is ablative because it follows in in a phrase showing location:

• in horto = in the garden

So the ending -o here is a sign of the ablative singular of a second-declension noun.

Because the verb ending already tells you the subject is third person singular.

• portat = he carries / she carries / it carries

Latin often does not need an explicit subject pronoun unless it wants special emphasis or contrast.

So instead of saying something like she carries, Latin can simply say portat, and if a noun like serva is already there, it is perfectly clear who the subject is.