Moja sestra pije čaj svako veče.

Because moja has to agree with sestra in gender, number, and case.

• sestra is feminine singular
• so the possessive my must also be feminine singular: moja

Compare:

• moj brat = my brother
• moja sestra = my sister
• moje dete = my child

So moja is the correct form because sestra is a feminine noun.

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

In Moja sestra pije čaj svako veče, the subject is moja sestra = my sister.

So:

• moja sestra = nominative, because she is the one who drinks
• čaj = object of the verb
• svako veče = time expression

Pije is the 3rd person singular present tense of the verb piti, which means to drink.

So:

• ja pijem = I drink
• ti piješ = you drink
• on/ona/ono pije = he/she/it drinks

Since moja sestra is she, Serbian uses pije.

This sentence therefore literally follows the pattern:

• Moja sestra = my sister
• pije = drinks
• čaj = tea
• svako veče = every evening

No — Serbian does not have articles like English a/an and the.

So čaj can mean:

• tea
• a tea
• the tea

The exact meaning depends on context.

In this sentence, English naturally translates it as tea, without needing an article in Serbian.

Čaj is in the accusative case because it is the direct object — the thing being drunk.

The verb piti takes a direct object, so the noun after it is usually in the accusative:

• pijem vodu = I drink water
• pije mleko = he/she drinks milk
• pije čaj = he/she drinks tea

Here is the useful detail: čaj is a masculine inanimate noun, and many masculine inanimate nouns have the same form in nominative and accusative singular.

So:

• nominative: čaj
• accusative: čaj

That is why the form does not visibly change.

Svako veče means every evening or every night in the sense of each evening.

Grammatically:

• svako = every, agreeing with a neuter singular noun
• veče = evening, a neuter singular noun

So svako veče is a matched phrase:

• svako jutro = every morning
• svako veče = every evening

This expression is commonly used to show habitual time — something that happens regularly.

In svako veče, the noun veče is in the accusative singular, used as a time expression.

Serbian often expresses time without a preposition when meaning something like:

• every day
• every morning
• every evening

So:

• svaki dan = every day
• svako jutro = every morning
• svako veče = every evening

For many neuter nouns like veče, the nominative and accusative singular forms look the same, so you do not see a change in the noun itself.

Also, svako is accusative singular neuter here, matching veče.

Yes. Svake večeri is also natural and means roughly the same thing: every evening.

The difference is mainly stylistic or structural:

• svako veče = literally every evening, very common and straightforward
• svake večeri = also common, using a different case pattern

A learner should definitely know that svako veče is completely normal and idiomatic.

Usually no. Because of svako veče, the sentence is understood as a habitual action:

• My sister drinks tea every evening
• My sister has tea every evening

So this is not normally about what is happening at this exact moment. It describes a routine or repeated action.

The verb is in the present tense, but the time phrase makes the meaning clearly habitual.

The given order is the most neutral and natural:

• Moja sestra pije čaj svako veče.

But Serbian word order is more flexible than English, so other orders are possible for emphasis or style, for example:

• Svako veče moja sestra pije čaj.
• Čaj moja sestra pije svako veče.
  This sounds more marked and emphasizes čaj.

So yes, the order can change, but the original sentence is the best default version for a learner.

Yes, you could say Sestra pije čaj svako veče, but the meaning changes slightly depending on context.

• moja sestra = my sister
• sestra = sister, but in context it might mean my sister, the sister, or even a nurse in some situations, since sestra can also mean nurse

So if you want to clearly say my sister, it is best to keep moja.

A helpful approximate pronunciation is:

• pije ≈ PEE-yeh
• čaj ≈ chai
• veče ≈ VEH-cheh

A few important points:

• č is like ch in church
• j is like English y in yes
• Serbian generally pronounces words quite consistently, so once you learn the sounds, spelling is very reliable

So the full sentence sounds approximately like:

MOH-yah SESS-trah PEE-yeh chai SVAH-koh VEH-cheh

Piti is imperfective, and yes, that matters.

Imperfective verbs are used for:

• habitual actions
• ongoing actions
• repeated actions
• general statements

Since this sentence means that the sister drinks tea regularly, the imperfective verb piti is exactly what Serbian needs here.

That matches the habitual meaning created by svako veče.

Because Serbian often omits subject pronouns when they are not needed.

The verb ending already helps identify the person, and here the subject is explicitly stated anyway:

• Moja sestra pije čaj svako veče.

Adding ona would usually be unnecessary unless you want special emphasis or contrast:

• Ona pije čaj, a brat pije kafu.
  = She drinks tea, and her brother drinks coffee.

So in the original sentence, leaving out ona is completely normal.