sagwareul daseos gae sassseupnida.

를 is the object particle. It marks 사과 (apple/apples) as the thing being bought.

So in 사과를 다섯 개 샀습니다, 사과를 means apples as the direct object of bought.

A few notes:

• 를 is used after nouns that end in a vowel.
• 을 is used after nouns that end in a consonant.

For example:

• 사과를 샀습니다 = (I) bought apples
• 빵을 샀습니다 = (I) bought bread

In Korean, when you count nouns, you usually need a counter word.

Here:

• 다섯 = five
• 개 = a very common counter for things/items

So 다섯 개 means five items.

Because 사과 is being counted, Korean normally says five apples as 사과 다섯 개 or 사과를 다섯 개 rather than just 사과 다섯.

개 is a very common general counter used for many everyday objects. Apples are things you can count with 개, so 다섯 개 is natural.

For apples, 개 is the normal choice in everyday Korean.

Examples:

• 사과 한 개 = one apple
• 사과 두 개 = two apples
• 사과 다섯 개 = five apples

Korean has two number systems:

• Native Korean numbers: 하나, 둘, 셋, 넷, 다섯...
• Sino-Korean numbers: 일, 이, 삼, 사, 오...

With many basic counters like 개, Korean usually uses native Korean numbers, especially for small numbers.

So:

• 다섯 개 = natural
• 오 개 = not natural in standard everyday Korean

This is why 다섯 개 is used instead of 오 개.

Yes. In Korean, the counted noun and its number-counter phrase often appear together, and there is some flexibility.

Your sentence:

• 사과를 다섯 개 샀습니다

A very common alternative is:

• 사과 다섯 개를 샀습니다

Both mean the same thing: (I) bought five apples.

Learners often first expect the number to come directly before the noun, as in English, but Korean commonly uses the pattern:

• noun + number + counter

So:

• 사과 다섯 개 = five apples

When particles are added, they may attach either to the noun phrase in different natural patterns depending on style and emphasis.

샀습니다 is the formal polite past tense of 사다, which means to buy.

Breakdown:

• 사다 = to buy
• past tense stem: 샀-
• formal polite ending: -습니다

So 샀습니다 means:

• bought
• or more naturally in a full sentence, (I) bought

It is a polite, formal style often heard in:

• announcements
• presentations
• customer service
• textbooks
• careful speech

This is due to a common Korean verb contraction in the past tense.

The verb 사다 combines with the past marker -았-:

• 사 + 았습니다

This contracts to:

• 샀습니다

So the shorter spoken and written form is 샀습니다.

The same kind of contraction happens in many verbs:

• 가다 → 갔습니다
• 보다 → 봤습니다
• 자다 → 잤습니다

No. Korean often leaves out the subject when it is already understood from context.

So 사과를 다섯 개 샀습니다 naturally means something like:

• I bought five apples
• (Someone) bought five apples

If you want to make the subject explicit, you can say:

• 저는 사과를 다섯 개 샀습니다 = I bought five apples
• 제가 사과를 다섯 개 샀습니다 = I bought five apples (with more emphasis on I)

Omitting the subject is very normal in Korean.

It can function as either, depending on context, but here the number makes it clearly plural in meaning.

• 사과 by itself can mean apple or apples
• 다섯 개 tells you the quantity is five

So the whole sentence clearly means five apples.

Korean nouns usually do not have to change form for plural the way English nouns do.

Usually, when giving an exact count, the counter should be included.

So:

• 사과를 다섯 개 샀습니다 = natural
• 사과를 다섯 샀습니다 = generally unnatural

Korean normally wants:

• number + counter

There are situations where the noun itself can be omitted if it is understood:

• 다섯 개 샀습니다 = I bought five (of them)

But if you keep the number, the counter is usually still needed.

In careful standard pronunciation, it is roughly:

사과를 다섣 깨 삳씀니다

A few pronunciation points:

• 다섯 is often heard like 다섣 before another word
• 개 can sound tense after certain consonant environments, so it may sound closer to 깨
• 샀습니다 is commonly heard roughly like 삳씀니다

You do not need to memorize this perfectly at the start, but it helps explain why spoken Korean may sound a little different from the spelling.

It is formal polite speech.

The ending -습니다 makes it sound:

• polite
• formal
• somewhat stiff in everyday casual conversation

So 사과를 다섯 개 샀습니다 is appropriate in situations like:

• speaking politely in a formal setting
• giving a report
• textbook example sentences

In everyday casual polite conversation, a person might more often say:

• 사과 다섯 개 샀어요

That is still polite, but less formal.