Я купил жетон в билетном автомате, потому что касса была закрыта.

Купил is the perfective past tense of купить, so it presents the action as a completed whole: I bought it / I ended up buying it.

That fits this sentence well, because the speaker is talking about one finished action: buying a token.

If you used покупал, that would be imperfective and would sound more like:

• a repeated action,
• a process,
• or background information.

So here:

• Я купил жетон... = I bought a token...
• Я покупал жетон... would usually not be the most natural choice for this specific completed event.

Because жетон is the direct object of купил, so it goes into the accusative case.

For an inanimate masculine noun in the singular, the accusative is usually the same as the nominative.

So:

• nominative: жетон
• accusative: жетон

If it were an animate masculine noun, the accusative would often match the genitive instead, but жетон is inanimate.

Because here в means in/at, expressing location, not motion.

With в:

• location → prepositional case
• motion into → accusative case

So:

• в билетном автомате = in/at the ticket machine
• в билетный автомат would mean into the ticket machine, which does not fit here

The speaker bought the token at the machine, so Russian uses the prepositional.

Because after в in the meaning of in/at, the noun takes the prepositional case.

So:

• nominative: автомат
• prepositional: в автомате

This is a very common pattern:

• в доме = in the house
• в магазине = in the store
• в автомате = in/at the machine

Adjectives in Russian must agree with the noun they describe in:

• gender
• number
• case

Here, автомате is:

• masculine
• singular
• prepositional

So the adjective must match:

• nominative masculine singular: билетный
• prepositional masculine singular: билетном

That is why you get:

в билетном автомате

Yes. Потому что is a fixed expression meaning because.

In this sentence it introduces the reason:

• Я купил жетон в билетном автомате, потому что касса была закрыта.
• I bought a token from the ticket machine because the ticket office was closed.

Learners sometimes try to analyze потому by itself, but in normal usage here потому что functions together as a conjunction.

Because закрыта here is the short-form adjective, and short forms are very commonly used to describe a state or condition, especially after быть.

So:

• касса была закрыта = the ticket office was closed

The long form закрытая / закрытой is used differently and would not be the normal choice here.

A useful rule of thumb:

• short form = often used for temporary/resulting states in predicate position
• long form = more descriptive/attributive, often before a noun or in other structures

So была закрыта is the natural way to say was closed.

Because касса is a feminine singular noun, and both parts must agree with it.

So:

• была = past tense feminine singular of быть
• закрыта = feminine singular short-form adjective

Compare:

• магазин был закрыт = the store was closed
• касса была закрыта = the ticket office was closed
• окно было закрыто = the window was closed

The endings change to match the gender of the noun.

Not necessarily. In transport or ticketing contexts, касса often means a ticket office, ticket booth, or sales window, not just a literal cash register.

So in this sentence, it most likely means the place where a person normally sells tickets or tokens.

That is why the sentence contrasts:

• buying from a machine
• because the ticket office/booth was closed

It could be omitted if the context already makes the subject clear.

Russian often drops personal pronouns when they are understood from the verb:

• Купил жетон в билетном автомате, потому что касса была закрыта.

That can still mean I bought a token..., because купил is masculine singular past tense and suggests a male speaker.

However, я is perfectly normal too. It may be used:

• for clarity,
• for emphasis,
• or simply because the speaker chooses to include it.

So both are possible, but Я купил... is very natural.

Yes, Russian word order is fairly flexible, though different orders can change the focus or emphasis.

The given sentence is neutral and natural:

Я купил жетон в билетном автомате, потому что касса была закрыта.

Possible alternatives:

• Потому что касса была закрыта, я купил жетон в билетном автомате.
  This emphasizes the reason first.
• Жетон я купил в билетном автомате, потому что касса была закрыта.
  This puts extra focus on жетон.

So the original order is probably the best default, but it is not the only possible one.

Russian has no articles like English a/an and the.

So:

• жетон can mean a token or the token
• касса can mean the ticket office or a ticket office

The exact meaning comes from context, not from an article.

In this sentence, English naturally uses:

• a token
• the ticket office

But Russian does not need separate words for that.

Касса is in the nominative case, because it is the subject of the clause:

касса была закрыта = the ticket office was closed

The subject of a sentence is typically in the nominative in Russian.

So:

• касса = nominative
• была закрыта = predicate agreeing with it

Literally, it is in the ticket machine, but in English the natural translation is often at the ticket machine or from the ticket machine, depending on context.

Russian often uses в with machines and places where English may choose a different preposition.

So in this sentence:

• Russian: в билетном автомате
• natural English: from the ticket machine or at the ticket machine

The exact English wording depends on style, but the Russian is perfectly normal.

Жетон means a token, usually a small coin-like object used for access or payment.

In transport contexts, it can refer to a token for:

• the metro,
• public transport,
• or another automated system.

A learner might expect билет (ticket), but жетон is a different word and refers specifically to a token, not a paper or digital ticket.

Because потому что introduces a subordinate clause giving the reason, and Russian normally separates that clause with a comma.

So:

• Я купил жетон в билетном автомате, потому что касса была закрыта.

This is standard Russian punctuation.

The second part:

• потому что касса была закрыта is the reason for the action in the main clause.