Philosophus dicit Alexandriam urbem doctam et claram esse.

Because this sentence uses indirect statement after dicit (says).

In Latin, after verbs of saying, thinking, knowing, hearing, and similar verbs, the content of the statement is often expressed with:

• an accusative subject
• plus an infinitive verb

So instead of saying something like The philosopher says that Alexandria is..., Latin says, more literally:

• The philosopher says Alexandria to be...

That is why Alexandria becomes Alexandriam.

For the same reason: this is an indirect statement.

In a normal direct statement, you would say:

• Alexandria urbs docta et clara est
  = Alexandria is a learned and famous city

But after dicit, Latin changes est to the infinitive esse:

• dicit Alexandriam ... esse
  = he says that Alexandria is ...

So esse is the infinitive to be, and it is the standard verb form used in this construction.

Because urbem is in apposition to Alexandriam.

That means it is another noun describing the same thing:

• Alexandriam = Alexandria
• urbem = city

So Latin is saying:

• Alexandriam urbem = Alexandria, a city

Since Alexandriam is accusative in the indirect statement, urbem must match it in case. Both refer to the same thing, so both are accusative singular feminine.

They agree with the noun they describe.

Here, doctam and claram describe urbem, and therefore also Alexandriam, since both nouns refer to the same city. Because urbem/Alexandriam is:

• feminine
• singular
• accusative

the adjectives must also be:

• feminine
• singular
• accusative

So we get:

• doctam
• claram

This is normal Latin adjective agreement.

Urbem means city, and it helps characterize Alexandria more explicitly.

The phrase:

• Alexandriam urbem doctam et claram esse

means literally something like:

• Alexandria to be a learned and famous city

Without urbem, the sentence could still work:

• Philosophus dicit Alexandriam doctam et claram esse

That would mean:

• The philosopher says that Alexandria is learned and famous

But adding urbem makes the structure more concrete and often sounds more natural in Latin, because the adjectives doctam and claram are then attached to city.

Yes, but not in the sense that the city itself studies books.

When Latin describes a city as docta, it usually means something like:

• learned
• cultured
• scholarly
• intellectually distinguished

So urbem doctam suggests a city known for learning, education, literature, or intellectual life.

In smoother English, you might translate it as:

• a cultured and famous city
• a learned and renowned city

depending on context.

Because Latin usually does not need a separate word for that in this kind of sentence.

English commonly says:

• He says that Alexandria is...

Latin usually uses the accusative + infinitive construction instead:

• dicit Alexandriam ... esse

So the idea of that is built into the grammar, not expressed by a separate word.

The sentence breaks down like this:

• Philosophus = the philosopher
• dicit = says
• Alexandriam = Alexandria (accusative subject of the indirect statement)
• urbem = city (in apposition to Alexandriam)
• doctam et claram = learned and famous (adjectives agreeing with urbem/Alexandriam)
• esse = to be

So the structure is:

• main clause: Philosophus dicit
• indirect statement: Alexandriam urbem doctam et claram esse

More literally:

• The philosopher says Alexandria to be a learned and famous city

More naturally:

• The philosopher says that Alexandria is a learned and famous city

Dicit is present tense, third person singular, from dicere.

It can mean:

• he says
• she says
• the philosopher says
• sometimes is saying, depending on context

In this sentence, the simplest translation is:

• The philosopher says...

The word order is fairly natural for Latin, but Latin word order is much freer than English word order.

A few things to notice:

• Philosophus dicit puts the main clause first.
• The whole indirect statement follows it.
• Alexandriam urbem keeps the two linked nouns together.
• doctam et claram comes before esse, which is very common in Latin.

Latin could rearrange parts of this sentence without changing the basic meaning, as long as the forms still show the grammatical relationships.

So word endings, not position alone, tell you who is doing what.

The direct statement would be:

• Alexandria urbs docta et clara est.

That means:

• Alexandria is a learned and famous city.

When this becomes dependent on dicit, Latin changes it like this:

• Alexandria → Alexandriam
• urbs → urbem
• docta → doctam
• clara → claram
• est → esse

So the direct statement is converted into an accusative-and-infinitive construction.

Not here.

If Latin wanted to say the city of Alexandria, it would normally use a different structure, often with a genitive or simply the proper name in apposition depending on context.

Here, Alexandriam and urbem are two accusative nouns referring to the same thing:

• Alexandria
• a city

So the sense is:

• Alexandria, a city
• or better in English, Alexandria is a city...

The sentence is not talking about one city belonging to Alexandria; it is identifying Alexandria as the city being described.