Dubito num Marcus meminerit quid magistra dixerit, quia is sine libro venit.

It helps to break it into parts:

• Dubito = the main clause, I doubt
• num Marcus meminerit ... = an indirect question, whether Marcus remembers ...
• quid magistra dixerit = another indirect question inside that clause, what the teacher said
• quia is sine libro venit = a causal clause, because he comes/came without a book

So the sentence is layered:

• I doubt
  • whether Marcus remembers
    • what the teacher said
  • because he comes/came without a book

Latin often packs clauses inside other clauses like this.

Here num means whether and introduces an indirect question.

After verbs like dubito (I doubt), Latin commonly uses num to mean whether:

• dubito num veniat = I doubt whether he is coming

A learner may know num from direct questions, where it often suggests the answer no. But in an indirect question like this, after dubito, it is best understood simply as whether.

So:

• Dubito num Marcus meminerit = I doubt whether Marcus remembers

Because num Marcus meminerit is an indirect question, and indirect questions in Latin normally take the subjunctive.

Compare:

• Direct question: Meminitne Marcus? = Does Marcus remember?
• Indirect question: Dubito num Marcus meminerit. = I doubt whether Marcus remembers.

So the subjunctive here is not because the action is unreal; it is there because the clause is grammatically an indirect question.

This is because memini is a special verb.

Memini, meminisse is a defective verb whose perfect forms have a present meaning:

• memini = I remember
• meminit = he/she remembers

So meminerit is morphologically a perfect subjunctive form, but with memini it often means he remembers rather than he has remembered.

That is one of the trickier things about this verb. English speakers often expect a normal present form, but Latin uses this special perfect-based system instead.

It is an indirect question meaning what the teacher said.

Here quid is the interrogative word what. It does not mean something here, and it is not the same as quod.

So the idea is:

• quid dixerit = what she said

This whole clause depends on meminerit:

• Marcus meminerit quid magistra dixerit = Marcus remembers what the teacher said

In other words, Marcus is remembering the content of the teacher’s words.

Because this is a question word, not a relative pronoun or conjunction.

• quid = what?
• quod can mean which, because, or that, depending on context

Since the clause is an indirect question, Latin uses the interrogative form:

• quid magistra dixerit = what the teacher said

If you used quod here, it would change the grammar and meaning.

For the same basic reason: quid magistra dixerit is also an indirect question, and indirect questions take the subjunctive.

There is also a time relationship here:

• Marcus is supposedly remembering something now
• the teacher’s speaking happened earlier

So Latin uses the perfect subjunctive dixerit to show action prior to the main verb of the indirect question.

Very roughly:

• meminerit = remembers
• dixerit = said earlier than that remembering

Because quia usually introduces a reason presented as a fact, so Latin normally uses the indicative.

• quia is sine libro venit = because he comes/came without a book

The speaker is giving a real reason for the doubt: Marcus arrived without a book, so maybe he does not remember what the teacher said.

So this is different from the indirect-question clauses:

• indirect question → subjunctive
• ordinary because clause with quia → usually indicative

By itself, venit can be ambiguous in spelling:

• present: he comes
• perfect: he came / has come

In classical pronunciation these were distinguished by vowel length, but ordinary printed Latin often does not mark that.

So you decide from context.

In this sentence, either idea could make sense depending on the translation you were given:

• because he comes without a book
• because he came/has come without a book

A beginner should not be surprised by this ambiguity; it is very common in Latin.

Latin often leaves subject pronouns out, because the verb ending already shows the person. But pronouns can be added for clarity or emphasis.

Here is means he and refers back to Marcus.

So:

• quia is sine libro venit = because he comes/came without a book

Using is makes the reference explicit: he, namely Marcus. It can help the reader keep track of the subject after the longer embedded clauses.

Libro is ablative singular because it follows sine.

The preposition sine always takes the ablative:

• sine libro = without a book / without the book

So this is simply a vocabulary-and-case pattern you have to learn:

• sine + ablative

Because Latin has no articles.

So:

• magistra can mean the teacher or a teacher
• libro can mean a book or the book

English requires an article, but Latin usually leaves that idea to context. The translation you choose depends on what makes sense in the passage.

Latin word order is much more flexible than English word order, because the endings show the grammatical relationships.

English depends heavily on order:

• The teacher saw Marcus is different from Marcus saw the teacher

Latin can move words around more freely because case endings and verb forms do the work.

In this sentence, the order helps with flow and emphasis:

• Dubito comes first to establish the main idea immediately.
• num Marcus meminerit gives the content of the doubt.
• quid magistra dixerit is placed right after meminerit, because that is what Marcus may or may not remember.
• quia is sine libro venit comes at the end as the explanation.

So the order is not random, but it is much less rigid than in English.