Quintus vir venit.

A basic parse is:

• Quintus: nominative singular masculine
• vir: nominative singular masculine noun
• venit: 3rd person singular verb

So the sentence has a singular subject and a singular verb.

If your book is treating Quintus as a name, then vir is another nominative word referring to the same person.
If your book is treating Quintus as fifth, then Quintus is an adjective agreeing with vir.

Because Latin can put two nouns in the same case when one identifies the other. This is called apposition.

So if Quintus is a person’s name, vir is telling you what Quintus is: a man. English often does something similar with commas, as in Quintus, the man, ...

If your text takes Quintus as fifth, then this is not apposition at all; it is simply adjective + noun, both in the nominative singular masculine.

It can be either, depending on context.

• Quintus can be a very common Roman personal name.
• quintus can also mean fifth.

Since you already have the meaning provided in your lesson, that tells you which one is intended here. In modern printed Latin, capitalization often helps too: Quintus usually suggests a name.

Because not all second-declension masculine nouns end in -us in the nominative singular.

Latin has masculine second-declension nouns such as:

• servus
• puer
• vir

So vir is perfectly normal. Its other forms show the declension more clearly, for example virī.

Because Latin usually builds the subject into the verb ending.

In venit, the ending -it tells you the verb is 3rd person singular, so Latin does not need a separate pronoun for he, she, or it unless the speaker wants extra emphasis or contrast.

It is the 3rd person singular present indicative active of venire.

That means it is the ordinary statement form: he/she/it comes.

Depending on context, English may also translate a Latin present as is coming, because Latin present tense often covers both simple present and progressive ideas.

Yes. If macrons are not written, the spelling can be ambiguous.

• venit = comes / is coming
• vēnit = came / has come

Many beginner books use macrons to keep these apart. If your lesson already gives the meaning, follow that meaning.

Because Latin has no definite or indefinite article.

So vir can mean:

• a man
• the man

Context tells you which is best in English.

This is very normal in Latin, and learners have to get used to supplying a/an/the only when translating into English.

No. Latin word order is much more flexible than English word order because the endings carry so much of the grammar.

So the same basic idea could appear in different orders, with different emphasis. For example, putting the verb first can make the action feel more prominent, while putting a noun first can spotlight that noun.

That said, subject ... verb is still a very common and natural order in simple sentences.

In a common classroom Classical pronunciation, a rough English approximation is:

• Quintus: KWIN-toos
• vir: roughly weer
• venit: WEH-nit

A couple of notes:

• Classical v sounds like English w
• Classical qu sounds like kw

So the whole sentence is roughly KWIN-toos weer WEH-nit.