Why Can すみません Also Mean “Thank You”?

Almost all of my students are surprised to learn that すみません can also express gratitude.

すみません is commonly known as the Japanese equivalent of “excuse me” or “I’m sorry.”

But in English, we don’t normally say “excuse me” to mean “thank you.” So why does this happen in Japanese?

To understand the logic behind it, let’s look at where the expression comes from.

すみません comes from the verb 済む(すむ).

済む can mean that something is finished, completed, or settled.

For example:

宿題が済みました。

The homework is finished.

そうじが済みました。

The cleaning is finished.

We also have the expression:

気が済みました。

I feel satisfied.

So how can すみません express gratitude?

In Japanese, when someone does something kind for you, you may feel that you owe them something in return—that the favor has not yet been fully “settled.”

This sense of indebtedness, together with gratitude for the other person’s effort, helps explain why すみません can also be used to express thanks.