Learn Hardcore Korean: munja-e dapjangeul neutge haeseo mian.

It’s casual/informal. 미안 is a clipped form of 미안해, so this is fine for close friends, same‑age peers, or younger people in texts. Avoid with elders, your boss, or strangers.

Why is it just 미안 and not 미안해?

미안 is a shortened, very casual way of saying 미안해. In speech or texting, people often drop -해 when the meaning is obvious. It’s a bit blunter than 미안해. If you want slightly softer casual, use 미안해.

How do I make this polite or formal?

Polite casual: 문자에 답장을 늦게 해서 미안해요.
Polite/formal: 문자에 답장이 늦어서 죄송합니다.
Very deferential (to a superior): 문자에 답장 드리는 게 늦어서 죄송합니다.

What does 문자에 mean here? Why the particle 에?

With 답장하다 “to reply,” Korean marks the target with -에: “reply to (something).” So 문자에 = “to the text (message).”

Reply to a person: 너한테/너에게 답장하다 (“reply to you”)
Reply to a message: 문자에 답장하다 (“reply to the text”)

Could I use 문자로 instead of 문자에?

Different meaning:

문자에 = “to the text (message)” (target)
문자로 = “by text message / via text” (means/instrument) Examples:
문자에 답장했어 = “I replied to the text.”
문자로 답장했어 = “I replied by text (rather than by call/email).”

Why is 답장을 marked with 을/를? Can I drop it?

답장 is the object of 하다 (“do a reply”), so 답장을 is standard. In casual speech you can drop the particle (답장 늦게 해서 미안) or even rephrase (늦게 답장해서 미안). All are common in texts.

What’s the difference between 답장을 늦게 해서 and 답장이 늦어서?

Both are natural:

답장을 늦게 해서 treats 답장하다 as an action: “I did the reply late.”
답장이 늦어서 treats 답장 as the subject of 늦다: “The reply was late.” Nuance is tiny; 답장이 늦어서 is extremely common.

What does -게 in 늦게 do?

-게 turns adjectives into adverbs. 늦다 (to be late) → 늦게 (“late-ly”), modifying 하다: 답장을 늦게 하다 = “to do the reply late.”

What is 해서 doing? Could I just say 늦게 해 미안?

-아서/어서 (해서) links a reason to a result: “Because I replied late, (I’m) sorry.”
Saying 늦게 해 미안 is unidiomatic. You need the connective: 늦게 해서 미안 or 늦어서 미안.

There’s no past tense marking. Is that okay?

Yes. In Korean, reason clauses with -아서/어서 often omit past tense even for past events. The apology is in the present. You would not normally say 미안했어 here; stick to 미안/미안해/미안해요/죄송합니다.

Are there other natural word orders?

Yes, for texting:

문자에 늦게 답장해서 미안.
문자 답장 늦어서 미안.
내 답장이 늦어서 미안. All are idiomatic.

Is 문자에 답장 the only way? What about 문자 답장?

Both are common:

문자에 답장하다 (verb + target marked by 에)
문자 답장 (compound noun “text reply”) as in 문자 답장이 늦다 (“the text reply is late”).

Any pronunciation tips?

문자 is pronounced roughly [문짜] (tensification of ㅈ).
답장 is [답짱] (tensification of ㅈ).
늦게 is [늗께] (the final ㅈ tenses the following ㄱ).
A smooth reading: “문-짜에 답-짱을 늗-께 해서 미안.”

How about spacing? Is 늦게해서 okay?

Write 늦게 해서 with a space. 늦게 (adverb) + 해서 (connective form of 하다). Don’t write 늦게해서 as one word.

Does 문자 mean only SMS? What about KakaoTalk?

문자 usually refers to SMS/text messages but is often used loosely for app messages in casual speech. For KakaoTalk, people also say 카톡 or 톡:

카톡 답장 늦어서 미안.
톡 답장 늦게 해서 미안.

How would I say this to my boss?

Use honorific/polite wording and often avoid “미안”:

문자에 답장이 늦어서 죄송합니다.
More deferential: 문자에 답장 드리는 것이 늦어서 죄송합니다.
Very clean: 답장이 늦었습니다. 죄송합니다.

Can I use 답변 or 회신 instead of 답장?

답장: everyday “reply,” esp. texts/DMs.
답변: “answer” to a question; more formal/content-focused.
회신: formal “reply/response,” common in business.
For texting a friend, stick with 답장.

Can I add intensifiers like 정말 or 너무?

Yes, to adjust tone:

Softer: 정말 미안. / 진짜 미안해.
Very casual: 너무 미안.
Be careful with 너무 in formal settings; use 정말/매우 죄송합니다 there.

Is the period after 미안 necessary?

No. In texts you’ll see 미안, 미안!, or nothing at all. Punctuation is optional in casual messaging.