Cum ventus frigidus per vicum flat, pueri domi manent.

Here cum means when.

It is being used as a conjunction introducing a clause: Cum ventus frigidus per vicum flat = When the cold wind blows through the street.

This is not the same as cum meaning with. When cum means with, it is a preposition and is followed by a noun in the ablative, not a whole clause.

You can tell by what comes after it.

• cum meaning with is followed by a noun, such as cum amico = with a friend
• cum meaning when is followed by a full clause with a verb, as in this sentence:
  • cum ventus frigidus per vicum flat

Since flat is a finite verb, this must be the conjunction cum = when.

Ventus means wind, and frigidus means cold.

Frigidus is an adjective modifying ventus, so the two words must agree in:

• gender: masculine
• number: singular
• case: nominative

So ventus frigidus means the cold wind or simply cold wind.

Latin often places the adjective after the noun, though other orders are also possible.

Because per takes the accusative case.

• vicus = street or neighborhood
• vicum = accusative singular

So:

• per vicum = through the street

This is a very common pattern in Latin: certain prepositions regularly require a specific case, and per always takes the accusative.

Pueri is nominative plural.

It is the subject of manent, so it must be in the nominative case.

• puer = boy
• pueri = boys or the boys

Since manent is plural, the subject must also be plural, which fits pueri.

Domi means at home.

This is a special form called the locative, used with certain words for places, especially domus.

So Latin often says:

• domi = at home

instead of:

• in domo = in the house

Both can make sense, but domi is the normal idiomatic way to say at home.

Both are present indicative active.

• flat = blows
• manent = remain or stay

In this sentence, the present tense expresses a general or habitual idea:

• When the cold wind blows through the street, the boys stay at home

So this is not necessarily describing one single event; it can mean whenever this happens, this is what they do.

Latin word order is more flexible than English word order because Latin uses case endings to show grammatical relationships.

A very common Latin pattern is to place the verb near or at the end of the clause:

• Cum ventus frigidus per vicum flat
• pueri domi manent

This does not change the meaning. It is simply a normal and natural Latin style.

Latin has no definite article and no indefinite article.

So:

• ventus frigidus can mean the cold wind or a cold wind
• pueri can mean the boys or simply boys

The exact sense is usually clear from context. English requires articles much more often than Latin does.

It can mean either, depending on context.

The basic meaning of maneo is remain or stay. In this sentence, English usually prefers stay:

• pueri domi manent = the boys stay at home

But understanding the core sense remain is still useful, because it helps you recognize related uses of the verb in other sentences.

Yes. Latin often allows either order.

You could also have:

• Pueri domi manent, cum ventus frigidus per vicum flat

That would still mean essentially the same thing: The boys stay at home when the cold wind blows through the street.

Latin authors choose clause order for style, emphasis, and rhythm, not because only one order is grammatically possible.

Here it is most naturally a time clause: when the cold wind blows.

Sometimes cum can introduce other kinds of clauses, including causal ones, but this sentence is straightforwardly temporal. Nothing in the sentence strongly suggests because; it simply gives the circumstance in time under which the boys stay home.

This is a normal Latin placement.

Latin often puts an important adverb or location word near the verb:

• pueri domi manent

This keeps domi closely connected with manent: they stay at home.

But other word orders could also be possible in Latin, depending on emphasis. For example, domi pueri manent might put a little more attention on at home.