Familia interlunio foris manet, dummodo tempestas non veniat.

Because familia is grammatically a singular noun in Latin, even though it refers to a group. Latin makes the verb agree with the grammatical number of the noun, so familia ... manet uses a singular verb.

This is similar to how English can sometimes treat a collective noun as singular, as in the team is winning.

Often yes, but it can be a little broader than the English word family. In Latin, familia can mean:

• a family
• a household
• the people belonging to one house
• in some contexts, even servants or slaves as part of the household

So family is a perfectly normal translation for a learner, but household is sometimes closer to the full Latin sense.

Interlunio is ablative singular of interlunium.

Here it is being used as an ablative of time when, which often does not need a preposition in Latin. Latin commonly says things like:

• nocte = at night
• aestate = in summer
• tertia hora = at the third hour

So interlunio means at the new moon or during the new moon period without needing a word like in.

Interlunium refers to the time of the new moon, literally the dark interval between moons.

So interlunio does not mean something like moonlight. It refers to the lunar phase when the moon is not visible or is newly dark.

Because foris means outside / outdoors in the sense of location, while foras means out / to the outside in the sense of motion toward a place.

A helpful contrast:

• foris manet = stays outside
• foras exit = goes बाहर / goes outside

Since manet means stays / remains, the sentence needs the adverb of location, foris.

Manet is:

• 3rd person singular
• present tense
• active
• from maneo, manere = to remain, stay

So it means he/she/it stays or remains.
Because the subject is familia, it is translated as the family stays/remains.

Dummodo means provided that, so long as only, or as long as in the sense of a condition.

It introduces a proviso: the main statement is true only on that condition.

So the structure is:

• main clause: Familia ... manet
• condition/proviso: dummodo tempestas non veniat

In natural English, that is something like The family stays outside, provided that ...

Because after dummodo meaning provided that, Latin normally uses the subjunctive.

So:

• venit = indicative, comes
• veniat = present subjunctive, may come / should come in form, though often translated simply as comes in English

English usually does not show this difference very clearly, so the translation may still just say provided that the weather does not come or more naturally provided that no storm comes.

Because the condition is a negative one: the family stays outside only if the bad weather does not come.

So:

• dummodo = provided that
• non = not
• veniat = come

Together: provided that the weather does not come.

The negation comes from non, not from dummodo itself.

Yes. Tempestas can mean:

• weather
• a season or time
• a storm
• bad weather

In many contexts, especially with a verb like veniat (comes), it can sound more natural to understand it as storm or bad weather rather than neutral weather.

So tempestas non veniat may be translated more naturally as:

• provided no storm comes
• provided the weather does not turn bad

That is often better English than a very literal provided that the weather does not come.

Latin word order is much more flexible than English word order because the endings show what each word is doing.

This order is quite natural:

• Familia — the topic/subject comes first
• interlunio — gives the time
• foris — gives the place
• manet — the verb closes the main clause
• dummodo tempestas non veniat — the condition comes afterward

So the sentence is not unusual; it is just arranged in a clear Latin way rather than an English one.

Not with exactly the same nuance.

• si means if
• dummodo means provided that

With si, the clause sounds like a more ordinary condition. With dummodo, it sounds like a restriction or requirement: the family remains outside only on this condition.

So dummodo is a little stronger and more specific than a simple if.