Praeco auctionem praedicat.

Praeco is the subject: the person doing the action.

Auctionem is the direct object: the thing being announced.

Praedicat is the verb: announces or proclaims.

So the structure is:

Praeco — auctioneer / public crier
auctionem — the auction
praedicat — announces

Because auctionem is in the accusative singular, the case normally used for a direct object.

The basic dictionary form is auctio or auctio, auctionis. In this sentence, the auction is the thing being announced, so Latin puts it in the accusative:

• auctio = auction sale
• auctionem = the auction sale, as the direct object

For an English speaker, this is one of the big differences in Latin: instead of relying mainly on word order, Latin often uses case endings to show a noun's job in the sentence.

Because praeco is simply the nominative singular form of that noun.

A native English speaker often expects Latin subjects to end in -us or -a, but that is only true for some nouns. Praeco belongs to the third declension, where nominative singular forms can end in many different ways.

So here:

• praeco = nominative singular, subject
• praeconem = accusative singular
• praeconis = genitive singular

The important lesson is: in Latin, you cannot identify a noun's case just by one ending pattern you learned from first-declension and second-declension nouns.

Praedicat is:

• present tense
• active voice
• indicative mood
• third person singular

It comes from the verb praedico, praedicare, meaning announce, proclaim, or advertise publicly.

So praedicat means:

• he announces
• she announces
• it announces

In this sentence, because the subject is praeco, the natural translation is the auctioneer announces.

Also, the ending -t is the usual marker for third person singular in Latin verbs.

Because Latin has no articles.

So praeco can mean:

• the auctioneer
• an auctioneer
• simply auctioneer

And auctionem can mean:

• the auction
• an auction

English requires an article in most sentences, but Latin does not. You choose the or a/an in translation from the context.

Yes. Latin word order is much more flexible than English word order, because the endings already show what each word is doing.

This sentence is:

Praeco auctionem praedicat.

That is a very natural Latin order, especially with the verb at the end.

But you could also see:

• Auctionem praeco praedicat.
• Praedicat praeco auctionem.

The basic meaning stays the same, because:

• praeco is still nominative
• auctionem is still accusative
• praedicat is still the verb

Changing the order usually changes emphasis, not the core meaning.

They are different words, but their meanings are closely connected.

• praeco is a noun: auctioneer, herald, public crier
• praedicat is a verb: announces, proclaims

So one names the person, and the other names the action.

For a learner, the key point is simply not to confuse them:

• praeco = who
• praedicat = does what

Yes, very often.

Because praedicat already means he/she/it announces, Latin can often omit an explicit subject if the context makes it clear.

So:

Auctionem praedicat.

could mean He/she is announcing the auction or The auctioneer is announcing the auction, depending on context.

In your sentence, praeco is included because the speaker wants to state the subject clearly.

In a reconstructed Classical Latin pronunciation, it is roughly:

PRY-koh owk-TEE-oh-nem PRY-di-kaht

A slightly more careful breakdown:

• praeco → PRY-ko
• auctionem → owk-TEE-o-nem
• praedicat → PRY-di-cat

A few useful points:

• ae is usually like ai in aisle
• au is like ow in cow
• c is always hard, like k
• the final -t in praedicat is pronounced

If you are learning Ecclesiastical Latin, the pronunciation will be somewhat different.