sensei ni orei wo iimasita.

Here, に marks the person the action is directed toward.

In this sentence, the action is 言いました (said / expressed), and 先生に means to the teacher.

So:

• 先生に = to the teacher
• お礼を言いました = expressed thanks / said धन्यवाद? no, in Japanese, gave thanks

With verbs of speaking, に often marks the person you speak to:

• 先生に話しました = I spoke to the teacher.
• 友だちに言いました = I said it to my friend.

を marks the direct object of the verb.

In お礼を言いました, the thing being expressed is お礼 (thanks / gratitude), so it takes を.

This pattern is:

• X に Y を 言う
• say Y to X

So here:

• 先生に = to the teacher
• お礼を = thanks / gratitude
• 言いました = said / expressed

Even though English often says thank someone, Japanese commonly uses the pattern お礼を言う, literally something like say thanks or express gratitude.

Because Japanese normally puts the verb at the end of the sentence.

The basic order is often:

• topic / subject
• time
• place
• indirect object
• direct object
• verb

So this sentence follows a very normal Japanese pattern:

• 先生に = to the teacher
• お礼を = thanks
• 言いました = said

In English, we might say I thanked the teacher or I expressed my thanks to the teacher, but Japanese usually saves the verb until the end.

The subject is omitted.

Japanese often leaves out the subject when it is already clear from context. So a sentence like this could mean:

• I thanked the teacher
• He thanked the teacher
• She thanked the teacher
• We thanked the teacher

The listener is expected to figure it out from the situation.

This is extremely common in Japanese. A full sentence with the subject included could be:

• 私は先生にお礼を言いました。 = I thanked the teacher.

But if 私は is already obvious, it is usually left out.

お礼 means thanks, gratitude, or an expression of thanks.

In this sentence, it does not mean a physical gift by itself. It means the act of expressing appreciation.

Common nuance:

• 礼 = thanks / gratitude / courtesy
• お礼 = a more polite or softened form

The phrase お礼を言う is a very natural way to say:

• to thank
• to express gratitude
• to say thank you

So even if the English translation is I thanked the teacher, the Japanese structure is built around saying gratitude.

The お is an honorific / polite prefix.

It often gets added to certain nouns to make them sound more polite, refined, or socially appropriate. 礼 by itself is a word, but お礼 is the common form in everyday polite Japanese.

This お does not change the core meaning very much. It mainly adds politeness.

Other common words with this kind of お are:

• お金 = money
• お水 = water
• お名前 = name

So お礼 is simply the normal polite form you are likely to hear.

言いました is the polite past form of 言う (to say).

Breakdown:

• 言う = dictionary form
• 言いました = polite past
• 言った = plain past

So the sentence is in polite style.

Compare:

• 先生にお礼を言いました。 = polite
• 先生にお礼を言った。 = plain / casual

Learners often see 〜ました in textbooks first because it is safe and polite in many situations.

It can match either translation in English.

A natural English translation could be:

• I thanked the teacher.
• I said thank you to the teacher.
• I expressed my gratitude to the teacher.

The Japanese wording is closer in structure to said thanks to the teacher, but in normal English, thanked the teacher is often the smoothest translation.

So the exact English wording may change, even though the Japanese meaning stays the same.

Normally, に is the natural choice here.

With verbs of speaking like 言う, the person receiving the words is usually marked with に:

• 先生に言う
• 友だちに話す

へ often emphasizes direction toward a place or target, but with a person in this kind of sentence, に is much more standard.

So:

• 先生にお礼を言いました。 = natural
• 先生へお礼を言いました。 = not the usual choice here

For a learner, it is best to use に with this pattern.

先生 can mean more than just teacher.

Depending on context, it can refer to:

• a teacher
• a doctor
• a professor
• sometimes other respected professionals

So 先生にお礼を言いました。 could mean:

• I thanked the teacher.
• I thanked the doctor.

The correct meaning depends on the situation. If your learning material glosses it as teacher, that is probably the intended meaning there.

Yes, Japanese word order is somewhat flexible, as long as the particles stay attached to the right words.

So these can both work:

• 先生にお礼を言いました。
• お礼を先生に言いました。

However, the first one is more neutral and natural in many textbook-style examples.

The most important thing is that the particles show the roles:

• 先生に = to the teacher
• お礼を = thanks

Because of the particles, Japanese does not depend on word order as strongly as English does. Still, the default pattern with the verb at the end is usually best for learners.

That is a very common question, especially because English says thank the teacher, where the teacher looks like the direct object.

But Japanese uses a different structure.

English:

• I thanked the teacher.

Japanese:

• I said thanks to the teacher.

So in Japanese:

• 先生に = to the teacher
• お礼を = thanks

The direct object is お礼, not 先生.

That is why を goes with お礼, not 先生.

Yes, it is a very common expression.

お礼を言う is a standard way to say:

• to thank
• to express thanks
• to say thank you

Japanese often uses these noun + を + verb combinations where English uses a single verb. For example:

• 勉強をする = to study
• 質問をする = to ask a question
• 電話をする = to make a phone call
• お礼を言う = to express thanks

So it is helpful to learn お礼を言う as a chunk, not just as separate words.