Postero die de bono communi in foro contio habetur, ut cives oratorem audiant.

Postero die is an example of the ablative of time when, which is used to say when something happens.

• die = day in the ablative singular
• postero = following / next, agreeing with die in case, number, and gender

So literally it is something like on the following day.

Latin often uses the ablative without a preposition for expressions of time:

• eo die = on that day
• prima luce = at first light
• tertia hora = at the third hour

Because postero comes from posterus, which means following or next, not after as a preposition.

So:

• postero die = on the next day / on the following day

If Latin wanted to say something more like after the day or afterward, it would use a different structure.

The preposition de takes the ablative case and often means:

• about
• concerning
• regarding

So:

• de bono communi = about the common good

Both words are ablative singular:

• bono = ablative singular of bonum
• communi = ablative singular of communis

They go together as a phrase meaning the common good.

Because de requires the ablative.

The basic dictionary form would be something like:

• bonum commune = the common good

But after de, both words must shift into the ablative:

• de bono communi

This is just normal adjective agreement in Latin:

• the adjective must match the noun in case, number, and gender

Because in with the ablative usually means in or on in the sense of location.

So:

• in foro = in the forum

This tells you where the assembly is held.

A very important contrast:

• in + ablative = location, in / on
• in + accusative = motion toward, into

For example:

• in foro = in the forum
• in forum = into the forum

Contio means a public gathering, assembly, or sometimes a public address.

In this sentence, it refers to a public meeting in the forum. It is the subject of habetur.

So the core idea is:

• contio habetur = an assembly is held

This is a very natural Roman political and public-life expression.

Because habere can be used idiomatically with events to mean to hold.

So:

• contio habetur literally = an assembly is held

Here habetur is:

• 3rd person singular
• present tense
• passive voice

It agrees with contio, which is singular.

This is similar to English expressions like:

• a meeting is held
• a speech is given

Because its subject, contio, is singular.

• contio = assembly (singular)
• habetur = is held (singular)

If the subject were plural, the verb would be plural too.

Here ut introduces a purpose clause.

So it means:

• so that
• in order that

The clause is:

• ut cives oratorem audiant
• so that the citizens may hear the speaker

This tells us the purpose of holding the assembly.

Because purpose clauses introduced by ut take the subjunctive in Latin.

So:

• ut ... audiant = so that ... may hear

audiant is:

• present subjunctive
• 3rd person plural
• from audire

This is not because the action is doubtful; it is because Latin uses the subjunctive regularly in purpose clauses.

Because audiunt would be the indicative, meaning simply they hear.

But after ut in a purpose clause, Latin needs the subjunctive:

• audiant = may hear

So the difference is grammatical:

• audiunt = statement of fact
• audiant = purpose/result-style subordinate clause form, here specifically purpose

The subject is cives.

• cives = the citizens
• audiant = may hear

So:

• ut cives oratorem audiant
• so that the citizens may hear the speaker

Even though cives could look the same in nominative plural and accusative plural, here it must be the subject because oratorem is clearly the object.

Because it is the direct object of audiant.

• cives = the citizens
• audiant = may hear
• oratorem = the speaker / orator

So the citizens are hearing the speaker, which makes oratorem accusative singular.

Not in the same way as in English. Latin word order is much more flexible because the endings show the grammatical relationships.

The sentence could be rearranged in several ways without changing the basic meaning very much.

This order, however, gives a natural flow:

1. Postero die = time
2. de bono communi = topic
3. in foro = place
4. contio habetur = main action
5. ut cives oratorem audiant = purpose

So the order helps emphasis and style, but the endings carry most of the grammar.

Most naturally, it goes with contio.

So the idea is:

• an assembly about the common good is held

It tells us the subject matter of the assembly.

Latin often places descriptive phrases before the main noun or verb, so it may feel slightly separated in English word order, but grammatically it fits very naturally with contio.

Yes. Since it is a purpose clause, good English translations include:

• so that the citizens may hear the speaker
• in order that the citizens may hear the speaker
• for the citizens to hear the speaker

The first two are the most literal and grammatically closest.