oneul wolgeubi gyejwa-e ipgeumdwaeseo gibuni johajyeosseo.

Because 이/가 marks the grammatical subject.

In 오늘 월급이 계좌에 입금돼서 기분이 좋아졌어, the thing that “got deposited” is 월급 (salary/pay), so 월급이 is natural.

• 월급이 입금되다 = the salary gets deposited
• 이/가 often marks the thing that undergoes the action or change

If you used 월급을, it would sound like 월급 is the object of another verb, which is not what is happening here.

에 is used here because it marks the location/destination where something ends up.

• 계좌에 입금되다 = to be deposited into an account

With money transfers, 에 is the standard and most natural particle for the receiving account.

Very roughly:

• 에 = in / into / at / to
• 로 = toward / by way of / as / with

So 계좌에 입금되다 is the normal expression.

입금되다 means to be deposited.

It comes from:

• 입금 = deposit
• 되다 = to become / to be done

So 입금되다 literally has the sense of to become deposited or to be processed as a deposit.

This is very common in Korean, especially in formal or financial language:

• 송금되다 = to be remitted/transferred
• 입력되다 = to be entered
• 등록되다 = to be registered

In English, it often sounds passive: was deposited.

It works a lot like a passive in English, but Korean learners often find it easiest to think of it as a very common 되다-based verb rather than forcing it into an English-style passive category.

In this sentence:

• 월급이 계좌에 입금되다 = the salary gets deposited into the account

So yes, the English translation is usually passive, but the Korean expression is just a standard, natural way to describe the event.

돼서 is the contracted conversational form of 되어서.

So:

• 입금되어서 → 입금돼서

Both are correct, but 입금돼서 is much more common in everyday speech and writing that sounds natural.

The same kind of contraction happens a lot:

• 되어 → 돼
• 하여 → 해

So 입금돼서 is just the normal shortened form.

Here -어서 shows a cause or reason.

So:

• 입금돼서 = because it was deposited / since it was deposited

The sentence means that the speaker’s mood improved because their salary was deposited today.

In many contexts, -아서/어서 can also connect events in sequence, but here the cause-and-effect meaning is the important one.

좋아졌어 means became good / got better / improved, so it emphasizes a change of state.

• 기분이 좋았어 = I felt good
• 기분이 좋아졌어 = I started feeling good / my mood improved

Because the salary was deposited, the speaker’s mood changed for the better. That is why 좋아졌어 fits so well.

Structure:

• 좋다 = to be good
• 좋아지다 = to become good / to improve
• 좋아졌어 = became good / improved

Because 기분 is the subject of 좋아졌어.

The sentence has two clauses:

1. 오늘 월급이 계좌에 입금돼서
2. 기분이 좋아졌어

In the second clause, what “became better” is 기분 (mood/feeling), so 기분이 is correct.

Korean often has multiple 이/가 markers in one sentence because each clause can have its own subject.

좋아졌어 is informal/casual speech.

It would be used with:

• friends
• close coworkers
• family
• people younger than you, depending on the relationship

A more polite version would be:

• 오늘 월급이 계좌에 입금돼서 기분이 좋아졌어요.

Same meaning, just more polite.

오늘 sets the time frame: today.

Korean often puts time expressions near the beginning of the sentence. That helps establish the context early.

So the overall flow is very natural:

• 오늘 = today
• 월급이 계좌에 입금돼서 = my salary got deposited into my account
• 기분이 좋아졌어 = so I felt better / my mood improved

This ordering is very typical in Korean.

Yes, but it is not exactly the same nuance.

• 월급을 받았어 = I received my salary
• 월급이 계좌에 입금됐어 = my salary was deposited into my account

The first focuses more on receiving pay in a general sense. The second focuses specifically on the money being deposited into the bank account.

If you want the banking/payment-processing nuance, 입금되다 is better.

Yes, it sounds very natural in everyday conversation.

It has a realistic spoken feel because of:

• 돼서 instead of 되어서
• 좋아졌어 in casual speech
• a very natural cause-and-effect structure

A native speaker could easily say this when talking about being happy that payday came through.

A polite version would be:

• 오늘 월급이 계좌에 입금돼서 기분이 좋아졌어요.

A slightly more formal/written version could be:

• 오늘 월급이 계좌에 입금되어서 기분이 좋아졌어요.

Differences:

• 좋아졌어 → 좋아졌어요 = more polite
• 입금돼서 → 입금되어서 = less contracted, a bit more formal

But in normal speech, 입금돼서 ... 좋아졌어요/좋아졌어 is usually the most natural.

It is usually pronounced close to:

• 입금돼서 → roughly ip-geum-dwae-seo

A few helpful points:

• 입금 is pronounced approximately 입끔 in connected speech because the final consonant influences the next sound
• 되어 contracts to 돼
• So the whole chunk sounds smooth and compact in actual conversation

You do not need to over-pronounce every written syllable separately. Listening practice will help this feel more natural.

Yes, in context it can.

Literally, it is closer to:

• my mood got better
• I started feeling good
• I felt happier

So while Korean says 기분이 좋아졌어 (my mood improved), natural English may simply say:

• I felt better
• I got happy
• I was happy
• I felt happier

The exact English wording depends on context, but the Korean clearly expresses a positive emotional change.