En somero la infanoj ludas sur la balkono ĝis malfrue, se la vetero restas varma.

En somero means in summer or during the summer.

There is no -n because en is a preposition, and in Esperanto prepositions normally take the basic form of the noun, not the accusative. So:

• en somero = in summer
• en la domo = in the house
• sur la balkono = on the balcony

Also, Esperanto often leaves out la in general time expressions like seasons when speaking broadly:

• en somero = in summer / in summertime
• dum vintro = during winter

If you said en la somero, that would more strongly suggest in the summer as a specific summer or a more definite context.

La infanoj means the children. Esperanto uses la when the speaker has specific children in mind, just like English uses the.

So here, the sentence is talking about a particular group of children, not children in general.

Compare:

• Infanoj ludas. = Children play. / Children are playing.
• La infanoj ludas. = The children are playing.

A learner should notice that Esperanto has only one definite article: la. It does not change for gender, number, or case.

In Esperanto, nouns end in -o, and the plural is made with -j.

So:

• infano = child
• infanoj = children

The structure is:

• infan- = root meaning child
• -o = noun ending
• -j = plural ending

This is one of the most regular parts of Esperanto grammar.

Ludas is the present tense form of ludi = to play.

In Esperanto, the present tense -as can cover both ideas that English often separates:

• play
• are playing

So la infanoj ludas could mean:

• the children play
• the children are playing

The exact meaning depends on context. In this sentence, because of En somero and ĝis malfrue, it sounds like a habitual action: In summer, the children play on the balcony until late...

Sur means on, while en means in.

A balcony is usually thought of as a surface or platform you are on, so Esperanto says:

• sur la balkono = on the balcony

Using en la balkono would sound like inside the balcony, which is not normally how people think about it.

This is very similar to English:

• on the balcony
• in the room

Because sur is a preposition, and the noun after it is normally not accusative.

So:

• sur la balkono = on the balcony

Esperanto uses -n mainly for direct objects and sometimes for direction/motion toward something.

For example:

• La infanoj ludas sur la balkono. = The children are playing on the balcony.
  
  • location, so no -n
• La infanoj kuras sur la balkonon. = The children run onto the balcony.
  
  • movement toward it, so -n can appear

That directional use is an important pattern in Esperanto.

Because malfrue is an adverb, and adverbs in Esperanto end in -e.

Here ĝis malfrue means until late.

Compare:

• malfrua = late, as an adjective
  
  • malfrua horo = a late hour
• malfrue = late, as an adverb
  
  • ili restas malfrue = they stay late

In this sentence, the word describes when they play, not a noun, so the adverb form is needed.

Ĝis means until or up to.

In this sentence:

• ĝis malfrue = until late

It marks the limit in time. You can also use it with other time expressions:

• ĝis morgaŭ = until tomorrow
• ĝis la vespero = until the evening
• ĝis la fino = until the end

It is a very common preposition.

The comma separates the main clause from the conditional clause.

Main clause:

• En somero la infanoj ludas sur la balkono ĝis malfrue

Conditional clause:

• se la vetero restas varma

So the structure is:

• The children play on the balcony until late, if the weather stays warm.

Using a comma before se is normal and helpful for clarity in Esperanto.

Yes, se means if and introduces a condition.

Examples:

• Se pluvas, ni restas hejme. = If it rains, we stay home.
• Se la vetero restas varma... = If the weather stays warm...

It is the standard word for if in conditional statements.

Here la vetero means the weather. Esperanto often uses la in places where English also uses the, especially for something understood from the situation.

So:

• la vetero = the weather

This is natural because the sentence refers to the weather in the relevant place and time.

Also, note that Esperanto usually uses vetero for weather, not tempo. English speakers sometimes guess tempo, but that word means time.

Because varma is describing the noun vetero.

• vetero = weather
• varma = warm

So la vetero restas varma literally means the weather remains warm.

After verbs like resti (to remain), Esperanto often uses an adjective to describe the subject:

• La akvo restas malvarma. = The water remains cold.
• Li fariĝis feliĉa. = He became happy.

You would use varme if you were describing the manner of an action, not the weather itself.

Because it agrees with vetero, which is singular.

In Esperanto, adjectives match the nouns they describe in number and case.

• la vetero = the weather
• varma = warm

If the noun were plural, the adjective would also be plural:

• la tagoj restas varmaj = the days remain warm

This agreement is a key feature of Esperanto grammar.

Yes. Esperanto word order is fairly flexible, as long as the grammar is clear.

You could also say:

• Se la vetero restas varma, en somero la infanoj ludas sur la balkono ĝis malfrue.

That means the same thing, though the emphasis shifts slightly. Putting se la vetero restas varma first makes the condition more prominent.

The original order sounds very natural too:

• first the general setting: En somero
• then the main action
• then the condition

Most likely it describes a habit or repeated situation.

Clues:

• En somero = in summer / during summer
• present tense ludas
• se la vetero restas varma = if the weather stays warm

Together, these suggest something like a general pattern: In summer, the children play on the balcony until late if the weather stays warm.

Esperanto present tense often covers habitual actions very naturally, without needing a special form.