Mane in solario sederunt et de Massilia, Carthagine, Sparta, atque Syracusis diu locuti sunt.

Mane means in the morning or early in the morning.

Grammatically, it is an adverb, not a noun in a case form. So it is not the subject, object, or anything like that; it simply tells you when the action happened.

In this sentence, mane modifies both actions:

• sederunt = they sat
• locuti sunt = they spoke

So the idea is that all of this happened in the morning.

In solario uses in with the ablative because it expresses location: in/on the terrace, balcony, or sun-room.

A useful rule is:

• in + ablative = in / on somewhere, showing place where
• in + accusative = into / onto somewhere, showing motion toward

So:

• in solario = on the terrace / in the sun-room
• If it meant into the terrace area, you would expect in with the accusative instead.

Sederunt is perfect active indicative, third person plural, from sedeo, sedere.

That means:

• third person plural = they
• perfect = a completed past action

So sederunt means they sat or they have sat, though in normal English here they sat is the natural translation.

Because loquor is a deponent verb.

A deponent verb:

• has passive-looking forms
• but an active meaning

So locuti sunt looks like a passive perfect, but it actually means they spoke or they talked.

It is made of:

• locuti = perfect participle
• sunt = they are/have as the helping verb

Together, for a deponent verb, this gives the perfect tense:

• locuti sunt = they spoke / they have spoken

This is one of the most important things for Latin learners to get used to.

Both verbs describe completed past actions.

Latin often uses the perfect for straightforward narration in the past:

• sederunt = they sat
• locuti sunt = they spoke

English sometimes distinguishes between they were sitting and they talked, but Latin here simply presents the actions as completed events. Depending on context, you might imagine:

• they sat there,
• and they talked for a long time.

The perfect does not always force a sharp sequence; it can simply narrate what happened.

De means about, concerning, or sometimes from/down from, depending on context.

Here it clearly means about:

• de Massilia, Carthagine, Sparta, atque Syracusis = about Marseilles, Carthage, Sparta, and Syracuse

After de, Latin uses the ablative case. So all the place names following de are in the ablative.

Because they belong to different declensions, and one of them is plural.

All of them are ablative after de, but they do not all form the ablative in the same way:

• Massilia → ablative singular Massiliā
  In ordinary printed Latin without macrons, this appears as Massilia.

• Carthago → ablative singular Carthagine
  This is a third-declension noun.

• Sparta → ablative singular Spartā
  Again, without macrons this appears as Sparta.

• Syracusae → ablative plural Syracusis
  This city name is commonly plural in Latin.

So even though the forms look different, they are all doing the same job after de.

Some place names in Latin are naturally plural in form, even though in English we treat them as a single city.

Syracusae is one of those. Its cases are plural:

• nominative: Syracusae
• genitive: Syracusarum
• dative/ablative: Syracusis

So after de, which takes the ablative, Latin uses Syracusis.

This is similar to how some ancient place names behave as plurals in Greek and Latin.

Diu is an adverb meaning for a long time.

It modifies locuti sunt, not sederunt. So the sense is:

• they sat on the terrace
• and they talked for a long time about those cities

Latin adverbs are often quite flexible in position, so diu can appear before locuti sunt without causing any problem.

Both et and atque mean and, but Latin often varies its connectors for style.

Here:

• et connects the two main actions: they sat and they talked
• atque joins the last item in the list: Massilia, Carthagine, Sparta, and Syracusis

So the sentence avoids repeating et in exactly the same way. In many contexts, et and atque are very close in meaning, though atque can sometimes feel slightly stronger or more emphatic.

The subject is understood from the verb endings.

• sederunt = they sat
• locuti sunt = they spoke

Both are third person plural, so the subject is they. Latin often leaves subject pronouns unstated when the verb ending already makes the person and number clear.

So the sentence does not need an explicit ei or illi for they.

Yes, but it is very normal Latin word order rather than something strange.

A few points:

• Mane comes first to set the time right away.
• in solario comes early to establish the setting.
• de introduces the topic of conversation before the verb locuti sunt.
• diu is placed just before locuti sunt, which neatly highlights how long they talked.

Latin word order is more flexible than English word order because the case endings show the grammatical relationships. So the order often reflects emphasis, style, or flow, not just grammar.