kosmuri naseo hyujiga piryohaeyo.

콧물 means snot, nasal mucus, or more naturally in everyday English, a runny nose depending on context.

It is made from:

• 코 = nose
• 물 = water/liquid

When combined, 코 + ㅅ + 물 becomes 콧물. That ㅅ is a linking sound that appears in some compound nouns.

So 콧물 is the noun for the stuff coming out of your nose.

Here, 콧물 is the subject of the verb 나다.

The expression is:

• 콧물이 나다 = for snot to come out / to have a runny nose

So 이/가 is used because 콧물 is the thing that is coming out.

Compare:

• 콧물이 나요 = My nose is running / Snot is coming out
• 콧물을 닦아요 = I wipe my nose / I wipe the snot

In the second one, 콧물 is the object being wiped, so 을/를 is used.

나서 comes from the verb 나다, which often means to come out, to appear, or to occur.

So:

• 콧물이 나다 = to have mucus come out of the nose / to have a runny nose

The form 나서 is 나다 + 아/어서.

Here, -아서/어서 means because or so:

• 콧물이 나서 = because my nose is running / since I have a runny nose

So the sentence connects two ideas:

• 콧물이 나서 = because my nose is running
• 휴지가 필요해요 = I need tissues

This is just a very natural Korean way of expressing the idea.

Korean often describes bodily symptoms with verbs like 나다:

• 땀이 나다 = sweat comes out / to sweat
• 피가 나다 = blood comes out / to bleed
• 열이 나다 = a fever comes up / to have a fever
• 콧물이 나다 = mucus comes out / to have a runny nose

So even if it feels less natural when translated literally into English, 콧물이 나다 is a normal Korean expression.

This is a very common learner question.

필요하다 works differently from English to need.
In Korean, the thing needed is usually marked with 이/가, not 을/를.

So:

• 휴지가 필요해요 = tissue is necessary / I need tissue
• 물이 필요해요 = water is necessary / I need water
• 시간이 필요해요 = time is necessary / I need time

Think of 필요하다 more like to be necessary than like a normal action verb such as to want or to buy.

That is why 휴지가 is correct here.

Both can refer to tissues, but there is a nuance.

• 휴지 often means paper, toilet paper, or tissue paper in a broad sense
• 티슈 usually means facial tissue more specifically

In everyday speech, if someone has a runny nose, 휴지 can still sound perfectly natural.
But 티슈가 필요해요 may sound more specifically like I need a facial tissue.

So in this sentence, 휴지가 필요해요 is natural and common.

Korean often omits the subject when it is obvious from context.

So 콧물이 나서 휴지가 필요해요 naturally implies something like:

• I have a runny nose, so I need tissues

But Korean does not need to say I if the listener can already understand who is being talked about.

You could add a subject if needed:

• 제가 콧물이 나서 휴지가 필요해요.

But in many situations, that sounds unnecessary because the meaning is already clear.

필요해요 is the polite informal style, often called 해요 style.

It is polite and very common in daily conversation.

Related forms:

• 필요해요 = polite everyday speech
• 필요합니다 = more formal
• 필요해 = casual, used with close friends or younger people

So 콧물이 나서 휴지가 필요해요 is polite and natural for many everyday situations.

Not always. -아서/어서 can connect clauses in a few different ways, including:

1. Cause/reason

   • 배가 아파서 집에 갔어요.
     = I went home because my stomach hurt.

2. Sequence of actions

   • 가게에 가서 물을 샀어요.
     = I went to the store and bought water.

In your sentence, it clearly shows reason:

• 콧물이 나서 휴지가 필요해요
  = Because my nose is running, I need tissues.

It is natural as a statement explaining your situation, but if you are directly asking someone for a tissue, Korean often uses a more direct request.

For example:

• 휴지 좀 주세요. = Please give me some tissue.
• 티슈 좀 주세요. = Please give me a tissue.
• 콧물이 나서 휴지 좀 주세요. = My nose is running, so please give me some tissue.

So:

• 휴지가 필요해요 = I need tissue(s)
• 휴지 좀 주세요 = Please give me tissue(s)

The first states a need; the second makes a request.

Yes. Korean nouns usually do not show singular vs. plural unless that distinction really matters.

So 휴지가 필요해요 could mean:

• I need a tissue
• I need some tissues
• I need tissue paper

The exact meaning depends on context.

If you really wanted to emphasize plural, you could say 휴지들이, but that would usually sound unnatural here. Korean normally leaves it unmarked.