chinguga oneureun deol bappeudaeyo.

-대요 is a reported-speech / hearsay ending.

In this sentence, 바쁘대요 comes from 바쁘다고 해요, which literally means (someone) says that they are busy or I heard that they are busy.

So 친구가 오늘은 덜 바쁘대요 means the speaker is passing along information, not necessarily stating it as their own direct observation.

A natural English sense is:

• My friend says they’re less busy today
• I heard my friend is less busy today

The exact nuance depends on context.

-은/는 is the topic marker, and here it gives 오늘은 a sense of as for today.

That often creates a slight contrast, such as:

• compared with other days
• unlike yesterday
• at least today

So 오늘은 덜 바쁘대요 feels like:

• As for today, they’re less busy
• Today, at least, they’re less busy

If you said 오늘 덜 바쁘대요 without -은, it would still be grammatical, but it would sound a bit more neutral and less contrastive.

-가 is the subject marker. It marks friend as the person who is less busy.

So in this sentence:

• 친구가 = the friend is the subject
• 오늘은 = today is the topic/time frame
• 덜 바쁘대요 = is said to be less busy

Using 친구가 is very natural here because the sentence is identifying who the reported information is about.

If you changed it to 친구는, the nuance would shift more toward as for my friend..., possibly with contrast.

덜 means less or not as much.

So:

• 덜 바쁘다 = to be less busy
• literally, to be busy to a lesser degree

It is often used when comparing something to:

• usual conditions
• another time
• another person
• expectations

Examples:

• 오늘은 덜 바빠요 = I’m less busy today
• 어제보다 덜 피곤해요 = I’m less tired than yesterday

Nothing is grammatically missing. In Korean, the comparison is often left unstated if it is obvious or not important.

So 덜 바쁘대요 could mean:

• less busy than usual
• less busy than yesterday
• less busy than expected
• less busy than before

If you want to make the comparison explicit, you can add it:

• 평소보다 덜 바쁘대요 = They say they’re less busy than usual
• 어제보다 덜 바쁘대요 = They say they’re less busy than yesterday

Without that extra phrase, Korean listeners just infer the comparison from context.

This is because 바쁘다 changes differently depending on what ending comes after it.

• 바빠요 comes from 바쁘다 + -아요
• 바쁘대요 comes from 바쁘다고 해요

The form 바빠요 happens because 바쁘다 is a ㅡ-irregular adjective when followed by -아/어요.

But -다고 is a different ending, so the adjective stays as 바쁘-:

• 바쁘다
• 바쁘다고 해요
• contracted: 바쁘대요

So 바빠대요 is not correct here.

It can mean either, depending on context.

Korean does not use articles like a or the, and it often leaves possessives like my unstated when they are obvious.

So 친구가 could mean:

• my friend
• a friend
• the friend

In everyday conversation, if no other context is given, English speakers often translate it as my friend because that is the most natural assumption.

The difference is mainly information source.

• 바빠요 = is busy / are busy
  This is a direct statement.

• 바쁘대요 = (someone says) is busy / I heard is busy
  This is reported information.

So:

• 친구가 오늘은 덜 바빠요 = My friend is less busy today
  The speaker states it directly.

• 친구가 오늘은 덜 바쁘대요 = My friend says they’re less busy today / I heard my friend is less busy today
  The speaker is relaying information.

It is polite everyday Korean.

The -요 ending makes it polite enough for normal conversation with:

• people you do not know very well
• coworkers
• acquaintances
• most everyday situations

It is not extremely formal. A more formal version would be something like:

• 친구가 오늘은 덜 바쁘다고 합니다

But 친구가 오늘은 덜 바쁘대요 sounds very natural in everyday speech.

Yes, especially because of 오늘은.

The -은 in 오늘은 often suggests a contrast such as:

• today is different
• today, at least
• today more than other days

So the sentence may subtly imply something like:

• usually the friend is busy, but today they are less busy
• other days may still be busy

This contrast is often soft and context-dependent, but it is definitely part of the nuance.

Not necessarily. -대요 is often used for reported content, not just exact quotation.

It can mean:

• they said that...
• I heard that...
• it’s said that...

So it does not always mean you are repeating the exact original words. It often just shows that the information came from another source.

In this sentence, the speaker may have:

• heard it directly from the friend
• heard it from someone else
• learned it indirectly and is passing it on

The important idea is that the speaker is reporting the information rather than simply presenting it as their own direct statement.