meoriga gireoseo achimmada du beoneun biseoyagessda.

Because 길다 is a descriptive verb/adjective meaning to be long, and in Korean the thing that is long is marked like the subject.

So:

• 머리가 길다 = the hair is long
• not 머리를 길다

A very common Korean pattern is:

• 눈이 크다 = the eyes are big
• 다리가 길다 = the legs are long
• 머리가 길다 = the hair is long

To an English speaker, this can feel strange because English often says I have long hair, but Korean usually says something closer to my hair is long.

Yes. 머리 can mean both head and hair, depending on context.

In this sentence, 머리가 길다 clearly means the hair is long, not the head is long.

Some common examples:

• 머리를 자르다 = cut one’s hair
• 머리가 아프다 = have a headache / the head hurts
• 머리가 길다 = have long hair

So context tells you whether 머리 means head or hair.

Here, -아서/-어서 means because or since.

So:

• 머리가 길어서 = because my hair is long / since my hair is long

This ending connects the reason to the result in the next clause:

• 머리가 길어서 아침마다 두 번은 빗어야겠다
• Because my hair is long, I guess I’ll have to comb/brush it at least twice every morning.

In other contexts, -아서/-어서 can also connect actions in a looser and then sense, but here it is clearly giving a reason.

It comes from the stem of 길다 plus -어서.

Step by step:

• dictionary form: 길다
• stem: 길-
• add -어서
• result: 길어서

This is a regular formation.

A few similar examples:

• 크다 → 커서 = because it is big
• 작다 → 작아서 = because it is small
• 예쁘다 → 예뻐서 = because it is pretty
• 길다 → 길어서 = because it is long

마다 means every when attached to a noun.

So:

• 아침 = morning
• 아침마다 = every morning

This is different from just 아침에, which means in the morning and does not necessarily imply repetition.

Compare:

• 아침에 빗어요 = I comb/brush my hair in the morning.
• 아침마다 빗어요 = I comb/brush my hair every morning.

So in your sentence, 아침마다 emphasizes that this happens regularly each morning.

The 은 adds emphasis or contrast. In this sentence, it gives a nuance like:

• at least twice
• twice, at minimum
• two times, anyway

So:

• 두 번 빗어야겠다 = I guess I’ll have to comb it twice.
• 두 번은 빗어야겠다 = I guess I’ll have to comb it at least twice.

This 은 often appears when the speaker is setting a minimum or contrasting with other possibilities.

So the sentence suggests something like:

• Because my hair is long, I’ll probably need to brush it at least twice every morning.

Yes, the full form could be 머리를 빗어야겠다, but Korean very often omits objects when they are obvious from context.

Here, the sentence already talks about 머리 and the verb 빗다 naturally goes with hair, so the object is easy to understand.

So both are possible:

• 머리를 빗어야겠다
• 빗어야겠다

The second one sounds natural because Korean often leaves out information that listeners can easily infer.

빗다 means to comb or brush hair.

Korean does not always separate these as strictly as English does. The exact English translation depends on the situation and what tool you imagine.

So this sentence could be translated as:

• I guess I’ll have to comb it at least twice every morning.
• I guess I’ll have to brush my hair at least twice every morning.

Both are reasonable.

-아/어야겠다 expresses a judgment or realization like:

• I should...
• I guess I have to...
• Looks like I’ll need to...

It is related to -아/어야 하다, which means have to / must.

Compare:

• 빗어야 한다 = I have to comb it.
• 빗어야겠다 = I guess I’ll have to comb it / looks like I should comb it.

The -겠다 part adds the speaker’s personal realization, decision, or impression. It sounds less like a blunt rule and more like the speaker is concluding this based on the situation.

In this sentence, the nuance is:

• Since my hair is long, I guess I’ll need to brush/comb it at least twice every morning.

They are similar, but the nuance is different.

• 빗어야 해요 = have to brush/comb it
• 빗어야겠다 = I guess I’ll have to / I should

빗어야 해요 sounds more direct and factual. 빗어야겠다 sounds like the speaker is realizing it on the spot or making a personal decision.

So this sentence feels a bit like self-talk:

• My hair is long, so I guess I’ll have to brush it at least twice every morning.

That reflective feeling comes from -겠다.

Yes, the implied subject is most naturally I.

Korean often omits subjects when they are understood from context. In this sentence:

• 머리가 길어서 = because my hair is long
• 빗어야겠다 = I guess I’ll have to comb/brush it

The ending -겠다 often sounds like the speaker’s own realization, so the sentence is most naturally understood as first person:

• I guess I’ll have to brush my hair at least twice every morning because it’s long.

Because of 두 번은, it sounds more like a minimum than a strict exact number.

So the nuance is not simply:

• exactly two times

but more like:

• at least two times
• probably two times or more

If the speaker wanted to sound more like a plain exact count, 두 번 without 은 would be more neutral.

So 두 번은 빗어야겠다 suggests:

• once is not enough
• two times is the minimum I’ll need