Moenia urbem defendunt.

Because moenia is normally a plural noun in Latin. It means city walls, fortifications, or ramparts, not just a single wall.

So Latin is imagining the defensive walls as a set or enclosure around the city. That is why the verb is also plural: defendunt = they defend.

Because urbem is the accusative singular form of urbs, meaning city.

In this sentence, the city is the direct object of the verb defendunt. The walls are doing the defending, and the city is the thing being defended.

• urbs = the city as a subject form
• urbem = the city as an object form

So:

• Urbs defendit = The city defends
• Moenia urbem defendunt = The walls defend the city

There are two main clues:

1. defendunt is plural, so its subject must be plural.
2. urbem is accusative, which marks it as the direct object.

That leaves moenia as the subject.

So the grammar tells us:

• moenia = subject
• urbem = object
• defendunt = verb

Defendunt means they defend or they are defending.

It comes from the verb defendere = to defend, ward off, protect.

The ending -unt tells you it is:

• present tense
• third person plural

So defendunt matches the plural subject moenia.

Latin usually has no word for the or a/an.

So moenia urbem defendunt can mean:

• The walls defend the city
• Walls defend a city
• The city walls defend the city

In normal context, English usually adds the where it sounds natural, but Latin itself does not include articles.

Yes, it could be different. Latin word order is more flexible than English because the noun endings show each word's job.

This sentence could also appear as:

• Urbem moenia defendunt
• Defendunt moenia urbem
• Moenia defendunt urbem

All of these can still mean basically The walls defend the city, because:

• moenia is nominative plural
• urbem is accusative singular
• defendunt is a plural verb

However, word order can change the emphasis. The version Moenia urbem defendunt is straightforward and clear.

Not exactly.

• murus usually means a wall, often a single wall
• moenia means city walls, fortifications, or defensive walls as a whole

So moenia is more specifically about the walls that protect a city. It is a very natural word in a sentence about defense.

Grammatically, it is plural. In meaning, it refers to the walls as a collective structure.

In English, we often think of the wall around a city as one thing. Latin more often thinks of it as the walls, a plural set of defenses.

So even if English might sometimes use a singular idea, Latin uses a plural noun and plural verb here.

Here moenia is nominative plural.

The nominative case is commonly used for the subject of the sentence. Since moenia is the thing doing the action of defending, nominative makes sense.

Also, because it is neuter plural, moenia has the nominative plural ending -a.

Yes. Depending on context, possible translations include:

• The walls defend the city
• The city walls defend the city
• The fortifications protect the city
• The ramparts defend the city

The basic grammar stays the same, but English may choose slightly different words for moenia depending on style and context.