Mia frato ne timas la najbaron, sed mia fratino timas lian bruon en la nokto.

Esperanto usually uses the simple verb timi for “to fear / to be afraid of”.

• Mia frato ne timas la najbaron.
  = My brother does not fear the neighbor / is not afraid of the neighbor.

So:

• timi = to fear, to be afraid (of)
• timas = present tense: fears / is afraid (of)

Forms like estas timigita (is frightened) or estas timanta (is fearing, progressive) are possible, but they add extra nuance and are not needed here. The normal, neutral way is just timas.

The -n marks the accusative case, used mainly for the direct object of a verb.

• Mia frato = my brother (subject)
• timas la najbaron = fears the neighbor (direct object → najbaron)
• mia fratino timas lian bruon = my sister fears his noise (direct object → bruon)

So:

• Basic noun: najbaro, bruo
• As direct object: najbaron, bruon

In Esperanto, you normally use la (the definite article) for specific, known things.

• la najbaron = the neighbor (a specific, known neighbor)

But when there is a possessive word (like mia, lia, ŝia, ilia, nia), that word already limits the noun strongly. In such cases, Esperanto usually omits la:

• lian bruon = his noise (not la lian bruon)

So:

• la najbaron — needed to make the neighbor definite.
• lian bruon — possessive lian already specifies which noise, so la is normally not used.

Lian means “his” and here it refers to the neighbor, not to the brother or the sister.

Reason:

• Subject in the first clause: Mia frato (my brother)
• Object in the first clause: la najbaron (the neighbor)
• Subject in the second clause: mia fratino (my sister)
• Possessor in lian bruon: contextually, the only masculine person being talked about is la najbaro.

Also, Esperanto has a special reflexive possessive sia (“one’s own”).
If we wrote:

• mia fratino timas sian bruon

then sian would refer back to mia fratino, so it would mean my sister fears her own noise.

By choosing lian, the sentence clearly says that the noise belongs to that other male person, i.e. the neighbor.

Adjectives and possessive pronouns in Esperanto agree with the noun’s case:

• lian bruon:

  • noun: bruon (accusative, direct object)
  • possessive: lia → agrees with bruon → lian

• mia frato:

  • noun: frato (subject, nominative)
  • possessive: mia → no accusative ending → stays mia

If mia frato became a direct object, both words would take -n:

• Mi vidas mian fraton.
  I see my brother.

Esperanto does not use a separate verb like “do” for negation. You simply put ne in front of the main verb:

• timas = fears / is afraid (of)
• ne timas = does not fear / is not afraid (of)

So:

• Mia frato ne timas la najbaron.
  My brother does not fear the neighbor.

No extra helping verb is needed; ne alone handles the negation.

The Esperanto verb timi is transitive, which means it takes a direct object without any preposition:

• timi iun = to be afraid of someone
• timi ion = to be afraid of something

So you say:

• timi la najbaron — to be afraid of the neighbor
  not timi de la najbaro.

Some English verbs need of, to, for, etc., but their Esperanto equivalents often use a direct object instead.

The usual neutral word order in Esperanto is Subject – Verb – Object (like in English):

• Mia frato (subject)
• ne timas (negated verb)
• la najbaron (object)

You can change the order, especially to put emphasis on a particular part:

• La najbaron mia frato ne timas.
• Mia frato la najbaron ne timas.

These are grammatically correct, but they sound more emphatic or stylistically marked.
The original order is the most neutral and the easiest for learners.

You can, but the meaning changes slightly.

• ne timas la najbaron
  → does not fear *the neighbor* (a specific neighbor)

• ne timas najbaron
  → more like is not afraid of *(any) neighbor in general*, or is not afraid of neighbors.

So la makes the neighbor definite and specific, while omitting la makes the idea more general.

Both are possible, but they differ in form and nuance:

• en la nokto

  • literally: in the night
  • sounds a bit more concrete or specific (e.g. during nighttime as a period)

• nokte

  • adverb formed from nokto
    • -e
  • means at night, by night, during the night in a more general adverbial way

You could say:

• Mia fratino timas lian bruon nokte.
  This is also correct and natural.

The original en la nokto simply chooses the prepositional style.

Sed means “but” and connects two clauses that contrast with each other:

• Mia frato ne timas la najbaron
  → one fact (the brother is not afraid)

• sed mia fratino timas lian bruon en la nokto
  → contrasting fact (the sister is afraid of his noise at night)

So sed introduces an opposition or contrast, just like English “but”.

Esperanto uses the suffix -in- to mark female. The root is neutral in theory, but in practice:

• frato = brother (male sibling)
• fratino = sister (female sibling)

Similarly:

• najbaro = neighbor (usually gender-neutral in modern usage)
• najbarino = female neighbor (if you specifically want to mark female gender)

They are different kinds of words, but in this sentence they both show adjectival forms:

• mia

  • possessive form of mi (I)
  • behaves like an adjective: mia frato, miaj fratoj, mian fraton, etc.

• fratino

  • noun: frat- (sibling) + -in- (female) + -o (noun ending)
  • base form ends in -o, but in mia fratino only mia ends in -a.

Careful not to mix them up:

• mia → always ends in -a (possessive adjective)
• fratino → main noun, normally ends in -o (and -n if accusative, -j if plural)