Horologium vetus tardius movetur, itaque pater non statim intellegit quo tempore nuptiae incipiant.

Because vetus is a 3rd-declension adjective: vetus, veteris.

Its nominative singular is vetus for masculine, feminine, and neuter alike. So:

• vir vetus = an old man
• femina vetus = an old woman
• horologium vetus = an old clock

By contrast, vetustum would come from vetustus, -a, -um, a different adjective meaning old, ancient, time-worn.

Tardius is a comparative adverb from tarde (slowly).

So:

• tarde = slowly
• tardius = more slowly / too slowly / slower than it should

It modifies the verb movetur, not the noun horologium. So it tells you how the clock moves.

A learner sometimes expects an adjective such as tardum, but that would describe the noun. Here Latin wants an adverb, because the idea is the clock is moving slowly, not the clock is slow as a noun-description.

Latin often uses a comparative when English would say something like:

• slow
• slowly
• too slowly
• slower than normal

So tardius movetur can mean it is moving more slowly than it should. With a clock, that is a very natural idea: it is running slow.

The comparison does not have to be stated explicitly. Latin can leave it understood.

Because movet means moves something: it is an active form and normally takes a direct object.

• movet horam would mean something like it moves the hour

But movetur is present passive, 3rd person singular:

• movetur = is moved / is moving

With a thing like a clock, Latin can use this form for the idea that the mechanism is going or operating. So even though the form is passive, the overall sense in English is often simply the clock is moving / running.

Itaque means and so, therefore, or so.

It connects the two clauses and shows that the second follows from the first:

• the old clock is running slow
• therefore the father does not immediately understand the time

So itaque marks result or consequence.

Quo tempore literally means at what time.

Here:

• tempore is ablative singular of tempus
• quo is also ablative singular neuter, agreeing with tempore

This is a common Latin way to ask about time:

• quo tempore? = at what time?

So the phrase is not random word order; it is a regular grammatical expression.

Latin can use both.

• quando = when
• quo tempore = at what time

Quo tempore is a bit more explicit and a little more formal-sounding. It makes the time idea very clear. In a teaching sentence, it is also useful because it shows how Latin can form an indirect question with an interrogative expression.

Because quo tempore nuptiae incipiant is an indirect question after intellegit.

The father does not understand at what time the wedding begins. That embedded at what time? is a question inside a larger sentence. In Latin, indirect questions normally take the subjunctive.

So:

• direct question: Quo tempore nuptiae incipiunt?
• indirect question: ... intellegit quo tempore nuptiae incipiant

That is why you get incipiant, not incipiunt.

Because after a present-tense main verb like intellegit, Latin uses the present subjunctive in an indirect question for something that is contemporaneous with or subsequent to the main verb.

So here the sense is roughly:

• he does not understand at what time the wedding is to begin / will begin

Latin does not need a special future subjunctive here. The present subjunctive does the job.

Because nuptiae, -arum is a plural-only noun in Latin. It means wedding, marriage ceremony, or nuptials, but it is grammatically plural.

So Latin says:

• nuptiae incipiunt / incipiant = the wedding begins

Even though English usually uses a singular word, Latin treats it as plural. That is why the verb is also plural: incipiant, not incipiat.

Because its subject is nuptiae, and nuptiae is grammatically plural.

So the agreement is:

• nuptiae = plural subject
• incipiant = plural verb

This is normal Latin subject-verb agreement, even though English might translate the whole idea with a singular noun, the wedding.

The word order is quite normal for Latin.

• Horologium vetus puts the subject first.
• tardius comes before movetur to emphasize how it moves.
• itaque introduces the consequence.
• pater non statim intellegit gives the main statement of the second clause.
• quo tempore nuptiae incipiant comes after intellegit as the indirect question.

Latin word order is more flexible than English because the endings show the grammatical roles. So the order is chosen more for style, emphasis, and clarity than for basic grammatical necessity.