Marcus respondet hoc participium ad tempus praeteritum pertinere, quia rem iam factam significat.

The main finite verb is respondet = Marcus answers / replies.

The rest of the sentence breaks down like this:

• hoc participium ad tempus praeteritum pertinere = what Marcus answers
• quia rem iam factam significat = the reason given

So the overall pattern is:

• Marcus respondet
• • an indirect statement
• • a quia clause explaining why

Because Latin very often does not use a separate word like English that after verbs of saying, thinking, knowing, and the like.

Instead, it commonly uses an accusative-and-infinitive construction:

• hoc participium = the subject of the reported statement
• pertinere = the infinitive

So English says:

• Marcus answers that this participle belongs to past time.

But Latin says, more literally:

• Marcus answers this participle to belong to past time.

That is normal Latin idiom.

It is an infinitive because it is part of that indirect statement after respondet.

In direct form, the statement would be something like:

• Hoc participium ad tempus praeteritum pertinet.
  = This participle belongs to past time.

When Latin reports that statement after a verb like respondet, it usually changes the finite verb to an infinitive:

• hoc participium ... pertinere

So pertinere is not the main verb of the whole sentence; it is the verb inside the reported statement.

Because participium is a neuter noun.

The demonstrative hic, haec, hoc must agree with the noun it modifies in gender, number, and case. Since participium is neuter singular, the correct form is hoc.

So:

• hic = masculine singular
• haec = feminine singular
• hoc = neuter singular

Therefore:

• hoc participium = this participle

In sense, it is the subject of the infinitive pertinere inside the indirect statement.

In Latin, the subject of an infinitive in this construction is normally put in the accusative. So here hoc participium is functioning as an accusative subject.

A beginner may not see that immediately because both words are neuter singular, and in neuter nouns/adjectives the nominative and accusative often look the same.

So the form is ambiguous by shape, but the syntax tells you its job.

The phrase pertinere ad means to pertain to, to belong to, or to relate to.

So:

• ad = to, toward, with reference to
• tempus praeteritum = past time

Because ad takes the accusative, both words are accusative singular:

• tempus = accusative singular neuter
• praeteritum = accusative singular neuter, agreeing with tempus

So ad tempus praeteritum pertinere means to pertain to past time.

Praeteritum is an adjective meaning past.

It agrees with tempus:

• tempus = time
• praeteritum = past

So the phrase literally means past time.

Although the word ultimately comes from a participial form, here it is simply functioning as an ordinary adjective modifying tempus.

Because rem is the direct object of significat.

• significat = signifies, indicates, means
• rem = a thing, matter, event, reality

So:

• rem significat = it signifies a thing / it indicates a matter

In smoother English, rem here often comes out as something or an action/event rather than a stiff literal thing.

Because it agrees with rem.

• res, rei is a feminine noun
• rem is its accusative singular form
• therefore any adjective or participle modifying it must also be feminine accusative singular

So:

• rem factam = a thing done / something done

factam is the perfect passive participle of facio:

• facio = I do, make
• factus, -a, -um = done, made

That participle strongly suggests completed action, which is why it helps explain past time.

Iam means already.

So:

• rem iam factam = a thing already done

This strengthens the idea of completion. The point is not just that something is done, but that it has already been done. That helps explain why the participle is connected with past time.

Because quia introduces a separate clause giving the reason:

• quia rem iam factam significat
  = because it signifies something already done

Latin does not turn every clause after an indirect statement into an infinitive. Here significat is simply the verb of the quia clause.

It is in the indicative because the sentence presents the reason straightforwardly as a fact.

Yes. Factam is a participle: specifically, the perfect passive participle of facio.

So this sentence contains the noun participium and also uses an actual participle, factam, in the explanation.

That is useful for learners because the sentence is not just talking about participles in theory; it also shows one in action.

Yes. Latin word order is much freer than English word order.

The phrase rem iam factam places:

• the noun first: rem
• the adverb next: iam
• the participle last: factam

This gives a natural emphasis to already done.

Other arrangements are possible in Latin, but this one is clear and idiomatic. The endings, not the position alone, show the grammatical relationships.