En decembro nia familio restas pli ofte hejme, ĉar estas malvarme kaj la tago estas mallonga.

Yes. En decembro means in December.

In Esperanto, en is commonly used for:

• location: en la domo = in the house
• time periods: en decembro, en somero, en 2025

So this works very much like English in December.

Also note that month names in Esperanto are normally not capitalized, so decembro is standard.

Because familio is grammatically a singular noun. It means family as one group.

So:

• nia familio = our family
• niaj familioj = our families

Even though a family contains many people, Esperanto treats familio as one unit here, just like English usually does.

That is why the verb is also singular:

• nia familio restas = our family stays/remains

Yes, here restas means stays or remains.

The verb is resti = to remain, stay.

So:

• restas hejme = stays at home / remains at home

In this sentence, restas suggests that the family spends more time staying at home rather than going out.

The ending -as shows present tense:

• resti = to stay
• restas = stays / is staying

Yes. Pli ofte means more often.

• ofte = often
• pli ofte = more often

In Esperanto, just like in English, you do not always need to say than before or than usual if the comparison is understood from context.

So:

• nia familio restas pli ofte hejme
  = our family stays home more often

The implied meaning is something like more often than in other times of the year or more often than usual.

Because hejme means at home, while hejmo means home as a noun.

This is a very common pattern in Esperanto:

• hejmo = home (noun)
• hejme = at home (adverbial form)

Examples:

• Mi estas hejme. = I am at home.
• Hejmo estas grava. = Home is important.

So in your sentence:

• restas hejme = stays at home

Yes. Ĉar means because.

It introduces the reason:

• nia familio restas pli ofte hejme = our family stays home more often
• ĉar estas malvarme kaj la tago estas mallonga = because it is cold and the day is short

So the structure is very straightforward: main statement + ĉar + reason

This is a very common learner question.

In Esperanto, weather and general conditions are often expressed with an adverb:

• Estas malvarme. = It is cold.
• Estas varme. = It is warm.
• Estas mallume. = It is dark.

Here, malvarme is an adverb, not an adjective.

Why? Because there is no real subject like it in Esperanto weather expressions. English uses a dummy subject:

• It is cold

Esperanto usually just says:

• Estas malvarme
  literally something like Is coldly, but naturally translated as It is cold.

By contrast, malvarma would describe a noun:

• La akvo estas malvarma. = The water is cold.
• La vetero estas malvarma. = The weather is cold.

So:

• Estas malvarme = the weather/atmosphere is cold
• Io estas malvarma = something is cold

Because Esperanto often leaves out the dummy subject that English requires.

English says:

• It is cold
• It is raining
• It is late

But that it does not really refer to anything. Esperanto does not usually need such a placeholder.

So you get:

• Estas malvarme. = It is cold.
• Pluvas. = It is raining.
• Estas malfrue. = It is late.

This is completely normal Esperanto.

La tago estas mallonga means the day is short.

Here are the two parts:

• la tago = the day
• mallonga = short

Why la? In Esperanto, la can be used for something understood generally in context. Here, the sentence is talking about December conditions, so la tago means the daytime/daylight period in that season.

Why singular? Using the singular here is a general statement, similar to English:

• The day is short in winter.

It talks about the day as a typical thing, not one specific calendar date.

You could also say:

• la tagoj estas mallongaj = the days are short

That would also be natural, but the original sentence uses the singular generic form.

Because they do different jobs.

• -a = adjective, used to describe a noun
• -e = adverb, used to describe a manner or a general condition

So:

• la tago estas mallonga
  mallonga describes tago, so it must be an adjective.

• estas malvarme
  malvarme expresses a general condition, so it is an adverb.

Compare:

• mallonga tago = a short day
• malvarma vetero = cold weather
• Estas malvarme. = It is cold.

Yes. Mallonga is made from:

• longa = long
• mal- = opposite

So:

• longa = long
• mallonga = short

This is one of the most useful patterns in Esperanto. The prefix mal- often creates the opposite meaning.

Examples:

• bona = good → malbona = bad
• granda = big → malgranda = small
• varma = warm → malvarma = cold
• longa = long → mallonga = short

Esperanto word order is fairly flexible, but this sentence uses a very normal, natural order.

Original:

• En decembro nia familio restas pli ofte hejme, ĉar estas malvarme kaj la tago estas mallonga.

This is easy and standard.

You could move some parts for emphasis, for example:

• Nia familio en decembro restas pli ofte hejme...
• Ĉar estas malvarme kaj la tago estas mallonga, nia familio restas pli ofte hejme.

Those are still understandable and natural.

However, for learners, the original order is a very good default:

1. time phrase
2. subject
3. verb
4. other information
5. reason with ĉar

The best natural English translation is stays at home more often.

• restas can mean stays or remains
• hejme means at home

So:

• stays at home more often is the most idiomatic choice

Remains home is not natural English; if you use remain, you would normally say remains at home.

So the most natural translation is:

• In December our family stays at home more often, because it is cold and the day is short.

Yes. Kaj means and.

Here it links two clauses:

• estas malvarme = it is cold
• la tago estas mallonga = the day is short

So:

• ĉar estas malvarme kaj la tago estas mallonga
  = because it is cold and the day is short

This is completely parallel to English.