seonsaengnimkke iyureul malhaesseoyo.

께 is an honorific particle meaning to or toward when the recipient is someone you want to show respect to.

So in 선생님께, it means to the teacher.

Korean has several particles for this idea:

• 한테 = to someone, casual
• 에게 = to someone, neutral/written
• 께 = to someone, honorific/respectful

Because 선생님 means teacher, using 께 sounds polite and appropriate.

를 is the object particle. It marks 이유 as the thing being said.

So the structure is:

• 이유를 = the reason as the object
• 말했어요 = said / told

Together, 이유를 말했어요 literally means said the reason or told the reason.

In more natural English, this is often translated as explained the reason or told them why.

말했어요 is the past polite form of 말하다 (to speak / to say / to tell).

Breakdown:

• 말하다 = to say
• 말했- = said
• -어요 = polite ending

So 말했어요 means said or told in a polite, everyday style.

This is polite, but not the most formal possible form.

Korean often omits the subject when it is already understood from context.

So 선생님께 이유를 말했어요 does not explicitly say I, he, she, or they. The subject is understood from the situation.

In many real conversations, this would naturally mean something like:

• I told the teacher the reason
• I explained the reason to the teacher

But grammatically, the sentence itself does not force I. Context decides.

Yes, but the level of politeness changes.

• 선생님에게 이유를 말했어요 = grammatically fine, neutral
• 선생님한테 이유를 말했어요 = understandable, more casual
• 선생님께 이유를 말했어요 = respectful and most appropriate for teacher

Since teachers are usually treated respectfully in Korean, 께 is the best choice here.

That is a very common learner question, and the answer is: both can work, but they have different levels of respect.

• 말했어요 = polite and normal
• 말씀드렸어요 = more humble and respectful toward the listener/recipient

Because the speaker is talking to a teacher, many native speakers would consider 선생님께 이유를 말씀드렸어요 more deferential.

Why?

• 말씀드리다 is the humble form used when I say something to a respected person
• It lowers the speaker’s action and raises the listener’s status

So:

• 선생님께 이유를 말했어요 = acceptable, polite
• 선생님께 이유를 말씀드렸어요 = more respectful

Both can often be translated as to say / to tell / to talk, but they feel a little different.

• 말하다 often focuses on saying something
• 이야기하다 can feel more like talk about or discuss

So:

• 이유를 말했어요 = I stated/told the reason
• 이유를 이야기했어요 = I talked about the reason

In this sentence, 말했어요 sounds very natural if the point is simply that the reason was given.

Yes. Literally, it is to say the reason, but in natural usage it often corresponds to English expressions like:

• tell the reason
• explain the reason
• say why

Korean does not always match English word-for-word. Even if English would often prefer explain, Korean can still use 말하다 naturally.

If you want a verb closer to explain, you could also say:

• 이유를 설명했어요 = I explained the reason

That sounds a bit more explicitly like explained.

Yes. Korean word order is flexible as long as the particles make the roles clear.

For example, these are all possible:

• 선생님께 이유를 말했어요
• 이유를 선생님께 말했어요

Both mean essentially the same thing.

Because 께 marks the recipient and 를 marks the object, Korean does not rely on word order as heavily as English does.

That said, the original order sounds very natural.

Sometimes, yes, especially in conversation. For example, people might say something like:

• 선생님께 이유 말했어요

But for learners, it is better to keep the particles:

• 선생님께 이유를 말했어요

Using the particles makes the sentence clearer and more standard.

Also, with a sentence like this, dropping 를 is more likely in casual speech than dropping 께, because 께 carries important honorific meaning.

Honorific verb forms in Korean depend mainly on the subject of the verb, not just on who receives the action.

In this sentence, the implied subject is probably I. Since the speaker is not honoring themself, you do not use a subject-honorific form like 말씀하셨어요.

Instead, respect toward the teacher is shown by:

• 선생님 itself
• the honorific particle 께
• possibly using the humble verb 말씀드렸어요

So the teacher is being respected, but not through a subject-honorific verb, because the teacher is not the one doing the speaking.

Possibly, depending on context. 이유 literally means reason, but in real situations it can sometimes sound like:

• reason
• explanation
• excuse

For example, if a student was late and said 선생님께 이유를 말했어요, the context might make it feel like I explained why or even I gave my excuse to the teacher.

The Korean word itself is still reason; the more specific nuance comes from the situation.

Not in the same structure.

• 이유를 말했어요 = told the reason
• 왜 means why, so it works in a different kind of sentence

For example:

• 왜 늦었는지 선생님께 말했어요 = I told the teacher why I was late

This is another very natural way to express the same general idea, but the grammar is different.
So 이유를 is a noun phrase (the reason), while 왜 introduces a why-clause.