Concordia apud bonos cives manet.

The subject is concordia.

It is in the nominative singular, and it means harmony, agreement, or concord. Since concordia is the thing that remains, it is the subject of manet.

Manet is singular because its subject, concordia, is singular.

• concordia = one harmony / concord
• manet = remains or stays

So the verb agrees with the subject in number: singular subject, singular verb.

Manet is the 3rd person singular present active indicative of maneo, manere, meaning to remain, to stay, or to continue.

So manet means:

• he/she/it remains
• in this sentence, it remains, referring to concordia

Because the preposition apud takes the accusative case.

So:

• bonos = accusative plural masculine of bonus
• cives = accusative plural of civis
• together: bonos cives = good citizens

This is not the direct object of the verb. It is accusative because it follows apud.

Here apud means something like among, with, or in the company of.

So apud bonos cives means:

• among good citizens
• with good citizens
• in the case of good citizens

It does not literally mean physical motion toward them. In this kind of sentence, it describes the group among whom the harmony remains.

A learner might expect bonis civibus because English often uses among good citizens, and Latin sometimes uses other constructions with the dative or ablative in different contexts.

But here the key point is simple: apud requires the accusative, not the dative or ablative.

So after apud, Latin must use:

• bonos cives, not bonis civibus

Because bonus is an adjective, and Latin adjectives must agree with the noun they describe in:

• gender
• number
• case

Here:

• cives = masculine plural accusative
• so the adjective must also be masculine plural accusative
• therefore: bonos cives

Even though bonus and civis belong to different declensions, they still agree in case, number, and gender.

Civis means citizen and is a 3rd-declension noun.

Its nominative singular is civis, and its accusative plural is also cives.

That is why the form here is cives. In this sentence it is plural and accusative because it follows apud.

The word order is fairly natural, but Latin word order is more flexible than English word order.

The sentence is:

• Concordia apud bonos cives manet.

A very literal structure is:

• Harmony among good citizens remains.

Latin could rearrange the words without changing the basic meaning, for example:

• Apud bonos cives concordia manet.
• Manet apud bonos cives concordia.

The endings show the grammar, so word order can be used for emphasis rather than basic sentence structure.

Latin has no articles like English the or a/an.

So concordia can mean:

• harmony
• the harmony
• a harmony

And boni cives could mean:

• good citizens
• the good citizens

The correct English translation depends on context, not on a separate Latin word for an article.

Sometimes apud can suggest something like in the eyes of, in the writings of, or among a certain group, depending on context.

In this sentence, the most natural meaning is still among good citizens or with good citizens. But a slightly broader interpretation such as in the case of good citizens is also possible.

So the phrase is about the sphere or group within which concordia exists or remains.

Grammatically, it is just a normal noun meaning harmony or concord. In Roman literature, however, abstract nouns like Concordia can sometimes be personified, even as a goddess.

In a simple sentence like this, the safest reading is just the abstract idea:

• Harmony remains among good citizens.

But a literary context could give it a more elevated or personified tone.