Discipuli ad forum veniunt, oratorem visuri.

The main clause is Discipuli ad forum veniunt = The students come to the forum.

Everything after the comma, oratorem visuri, adds extra information about why they are coming.

Visuri is the future active participle of video, videre = to see.

So visuri literally means about to see or going to see.

In this sentence, oratorem visuri means something like:

• to see the speaker
• intending to see the speaker
• about to see the speaker

With verbs of motion like veniunt (they come), this participle often expresses purpose.

Because in Latin, the future participle can be used with a verb of motion to show purpose.

So:

• veniunt = they come
• oratorem visuri = with the intention of seeing the speaker

A natural English translation is:

• The students come to the forum to see the speaker.

Even though visuri literally means about to see, English usually prefers to see here.

Because it agrees with discipuli.

• discipuli = students (masculine plural nominative)
• visuri = about to see (masculine plural nominative)

The participle describes the students, so it must match them in:

• number: plural
• gender: masculine
• case: nominative

Because visuri agrees with discipuli, not with oratorem.

That is a very common point of confusion.

• discipuli is nominative plural, so the participle is visuri
• oratorem is accusative singular because it is the object of seeing

So the grammar is:

• discipuli ... visuri = the students ... about to see
• oratorem = the speaker as the thing seen

Because oratorem is the direct object of visuri.

The verb videre takes a direct object in the accusative:

• oratorem videre = to see the speaker

So in this sentence:

• oratorem = the speaker is the person the students are going to see

Because ad takes the accusative case when it means to or toward.

So:

• ad forum = to the forum

This is the normal way in Latin to express motion toward a place.

Forum usually means the forum, that is, the public square or marketplace area in a Roman town.

So ad forum veniunt means they are coming to the public square/forum.

It does not mean an internet forum, of course; it means a physical public place.

Veniunt is present tense, third person plural, from venio, venire.

It means:

• they come
• or, depending on context, they are coming

Both can be reasonable in English.

Not especially in a grammatical sense.

Latin manuscripts originally had little or no punctuation, and modern editors add punctuation to help readers.

The comma here simply helps separate:

• the main action: Discipuli ad forum veniunt
• the purpose phrase: oratorem visuri

So it is helpful, but the grammar does not depend on it.

Yes.

Latin has more than one way to express purpose. For example, a purpose clause with ut is often possible in other contexts.

But after a verb of motion, the future participle like visuri is a neat and idiomatic way to say:

• coming to see
• going in order to see

So this construction is perfectly normal and worth recognizing.

The words are arranged as:

• Discipuli = students
• ad forum = to the forum
• veniunt = come
• oratorem visuri = about to see the speaker

Latin word order is flexible, so the sentence is not built in exactly the same order English would use.

A very literal version would be:

• The students come to the forum, about to see the speaker.

A more natural English version is:

• The students come to the forum to see the speaker.

Because this is a common Latin pattern:

• verb of motion
  • future participle

The idea is:

• they come ... intending to see
• they go ... intending to do something
• they send someone ... about to do something

So when you see veniunt followed by a future participle, it is a good clue that the participle expresses the purpose of the motion.

You should not memorize visuri by itself as a separate word. Learn it from the verb video, videre, vidi, visum.

From that verb, the future active participle is formed as:

• masculine singular: visurus
• feminine singular: visura
• neuter singular: visurum

Here you have the masculine nominative plural form:

• visuri

So when parsing it, think:

• visuri ← from visurus ← from video

Here is a compact parsing:

• Discipuli — nominative masculine plural of discipulus, subject, the students
• ad — preposition taking the accusative, to/toward
• forum — accusative singular of forum, object of ad, the forum
• veniunt — 3rd person plural present active indicative of venio, they come
• oratorem — accusative singular of orator, direct object of visuri, the speaker/orator
• visuri — nominative masculine plural future active participle of video, agreeing with discipuli, about to see / going to see

The most natural translation is:

The students come to the forum to see the speaker.

If you want to stay closer to the Latin grammar, you could also say:

The students come to the forum, intending to see the speaker.