Pre posla moja majka često pere ruke u kupatilu.

Because the preposition pre meaning before requires the genitive case in Serbian.

• Basic noun: posao = work / job
• Genitive singular: posla

So:

• pre posla = before work

This is a very common pattern:

• pre ručka = before lunch
• pre škole = before school
• pre sastanka = before the meeting

So the important thing to remember is: pre + genitive.

Moja majka is in the nominative case because it is the subject of the sentence — the person doing the action.

• majka = mother
• moja = my

The adjective/pronoun moja agrees with majka in:

• gender: feminine
• number: singular
• case: nominative

So:

• moja majka = my mother as the subject

If the role changed, the form could change too. For example, in another sentence you might see different case forms of majka.

Because the subject is moja majka = my mother, which is third person singular.

The verb is prati = to wash. Its present tense forms include:

• ja perem = I wash
• ti pereš = you wash
• on/ona/ono pere = he/she/it washes
• mi peremo = we wash
• vi perete = you wash
• oni/one/ona peru = they wash

Since majka = she, the correct form is pere.

Često means often, and in Serbian adverbs like this commonly go before the verb.

So:

• moja majka često pere ruke = my mother often washes her hands

That said, Serbian word order is more flexible than English, and you may hear other arrangements for emphasis. For example:

• Moja majka pere ruke često — possible, but less neutral
• Često moja majka pere ruke — possible, with a different emphasis

The version in your sentence sounds natural and neutral.

In Serbian, when talking about body parts, it is very common to omit the possessive if it is already obvious whose body part it is.

So Serbian naturally says:

• pere ruke = washes hands

Even though English usually says:

• washes her hands

Since the subject is moja majka, it is already clear that these are her hands.

You can say svoje ruke, but it is usually unnecessary unless you want emphasis or contrast.

Good question. In Serbian, washing a body part is often expressed with a normal transitive verb + body part, not necessarily with se.

So:

• pere ruke = washes hands / washes her hands

This is perfectly natural Serbian.

You may also encounter reflexive-style expressions in some contexts, but with body parts, Serbian very often simply uses the object directly:

• perem lice = I wash my face
• pere ruke = she washes her hands

So the sentence is natural exactly as it is.

Ruke is in the accusative plural, because it is the direct object of the verb pere.

She is washing what? → ruke = hands

For the noun ruka:

• singular nominative: ruka
• plural nominative: ruke
• plural accusative: ruke

So here the form ruke happens to look the same as the nominative plural, but in the sentence its function is accusative plural.

Because u can mean either in or into, and the case depends on whether there is:

• location → locative
• movement toward a destination → accusative

Here the meaning is location:

• she washes her hands in the bathroom

So Serbian uses:

• u + locative
• u kupatilu = in the bathroom

Compare:

• u kupatilu = in the bathroom
• u kupatilo = into the bathroom

That second form would imply movement into the room.

The base form is kupatilo = bathroom.

In the sentence, after u expressing location, it becomes locative singular:

• kupatilo → kupatilu

So:

• u kupatilu = in the bathroom

This is a common neuter noun pattern in Serbian.

Pere comes from the imperfective verb prati, which is used for:

• repeated actions
• habitual actions
• ongoing actions

Since the sentence contains često = often, it describes a habit, so the imperfective is the natural choice:

• često pere ruke = she often washes her hands

A perfective verb like oprati / opere would usually refer to a completed single action, not a habit.

So for habitual meaning, pere is exactly right.

Yes. Serbian word order is relatively flexible because case endings show grammatical roles.

Your sentence is a natural neutral version:

• Pre posla moja majka često pere ruke u kupatilu.

But other versions are possible, depending on emphasis:

• Moja majka često pere ruke u kupatilu pre posla.
• Često moja majka pere ruke u kupatilu pre posla.
• U kupatilu moja majka često pere ruke pre posla.

These do not all feel equally neutral, but they are understandable. Serbian uses word order a lot for focus, topic, and style, more than English does.

Because Serbian has no articles.

English distinguishes:

• a bathroom
• the bathroom

Serbian does not use separate words for that. Instead, definiteness is understood from:

• context
• word order
• general meaning

So u kupatilu can mean in the bathroom here because the context makes it natural.

Usually pre posla is understood as the general time expression before work, similar to English before work.

It normally refers to the period before someone goes to work or before the workday begins, not necessarily to a very specific single job event.

So in everyday language, it sounds natural and idiomatic.