Marcus quaerit utrum “quis” pronomen interrogativum sit.

Utrum introduces an indirect yes/no question, so here it means whether.

After a verb like quaerit, Latin often marks the thing being asked with utrum:

• Marcus quaerit utrum ... sit = Marcus asks whether ... is

If there were two alternatives, Latin would often use utrum ... an ... = whether ... or .... But when there is only one clause, utrum by itself is enough.

Because utrum quis pronomen interrogativum sit is an indirect question, and indirect questions in Latin normally take the subjunctive.

So Latin distinguishes:

• direct question: utrum ... est? or estne ... ?
• indirect question: utrum ... sit

The present subjunctive sit is also the expected tense here because the asking and the being are happening at the same time.

Yes.

That matters because Latin uses different constructions for the two:

• Indirect question: interrogative word or particle + subjunctive
  
  • quaerit utrum ... sit
• Indirect statement: accusative + infinitive
  
  • for example, Marcus dicit eum venire

Since Marcus is asking whether something is true, Latin uses an indirect question, not an indirect statement.

Because the sentence is talking about the form quis itself.

This is called a metalinguistic use: the word is being mentioned as a word. It is not being used to ask who? or what? about some person or thing. English does the same thing in a sentence like Who is an interrogative pronoun.

In print, teachers often mark a mentioned word with bold, italics, or quotation marks so that learners can see that the word itself is the topic.

It is nominative because it is the subject of sit in the indirect question.

The clause means, in structure, whether quis is an interrogative pronoun. So:

• quis = subject
• sit = verb
• pronomen interrogativum = predicate nominative

Also, when Latin words are cited by themselves, they are often given in their basic dictionary form, which for nouns and pronouns is usually the nominative singular.

Because after a form of esse, the noun that identifies or classifies the subject is normally in the nominative too.

So in:

• quis ... sit pronomen interrogativum

both expressions are nominative because they refer to the same thing:

• quis = the thing being discussed
• pronomen interrogativum = what it is

This is called a predicate nominative.

Quaerit is:

• 3rd person singular
• present tense
• active voice
• indicative mood

Its subject is Marcus, so Marcus quaerit means Marcus asks or Marcus inquires.

Depending on context, quaerere can also mean to seek or to investigate, but here asks / inquires fits the grammar well.

Because an is usually used when Latin gives a second alternative.

For example:

• utrum hoc verum sit an falsum = whether this is true or false

But if there is only one yes/no clause, utrum alone is perfectly normal:

• utrum quis pronomen interrogativum sit = whether quis is an interrogative pronoun

Not in standard Classical Latin, if you want the normal way to express an indirect question.

Si primarily means if in a conditional sense. For an indirect question meaning whether, Classical Latin normally prefers utrum or another interrogative word.

So for a learner, utrum ... sit is the pattern to remember here.

No. Latin word order is flexible, because endings do much of the grammatical work.

Still, this sentence has a very natural order:

• Marcus quaerit = the main statement first
• utrum ... sit = the indirect question after it
• sit at the end = a very common position for the verb in a subordinate clause

So the order is not the only possible one, but it is clear and idiomatic.