죄송합니다 vs 미안해요, 감사합니다 vs 고마워요

The hinge

Sorry and thanks in Korean name the reason first, then the feeling. The link is always -아서/어서. Not -고. Not a past tense stuffed into the reason. Not 니까.

늦어서 죄송합니다.
neujeoseo joesonghamnida — I’m sorry I’m late.

늦다 takes -어서 because the stem vowel is not ㅏ or ㅗ. 죄송합니다 is 합니다체 — a shop, a teacher, someone you have just met. A classmate gets 해요체: 늦어서 미안해요.

What not to write

What you must not write:

• 늦었어서 — -아서/어서 never takes past. The lateness is already the reason; 었 is illegal there.
• 늦고 죄송합니다 — -고 lists another action. Sorry is not a second chore.
• 늦으니까 죄송합니다 — 니까 is a reason, but not this reason. Apologies refuse it.

Thanks

Thanks uses the same hinge.

도와줘서 감사합니다.
dowajwoseo gamsahamnida — Thank you for helping.

도와주다 → 도와줘 + 서. 감사합니다 is the formal default. 고마워요 is the everyday line: 고맙다 is ㅂ-irregular, so ㅂ drops and you get 워, then 요. 고맙습니다 is still 합니다체, built on that same 고맙- stem. 수고하셨습니다 thanks someone for a finished shift, not for a pen — that page is a different job.

The room

There is a middle sorry: 죄송해요. Same 죄송- stem, 해요체 ending. It is milder than 죄송합니다 and still more careful than 미안해요. A shop you visit often can take it. A first meeting with a teacher still wants 죄송합니다.

When someone thanks you, 아니에요 closes it. 괜찮아요 can take an apology the same way — it tells the other person to drop the weight. 천만에요 exists in textbooks; it is not the line you hear at a counter. Do not invent a new thank-you to answer a thank-you.

Pick the word by the room, not by how sorry you feel. A stranger and a counter get 죄송합니다 / 감사합니다. A friend gets 미안해요 / 고마워요. The hinge does not change when the room does. 바빠서 미안해요, never 바빴어서.

Company notices reuse 죄송합니다 at the end of a different grammar. This page is a person talking to a person. The reason still comes first, and it still comes on -아서/어서.