すみません。

Sumimasen.

Excuse me / sorry / thank you.

Word for word

“It does not end (I cannot repay).”

Politeness: Polite

です/ます style. The safe default with strangers, shop staff and colleagues.

When you would say it

Getting attention, apologising lightly, or thanking someone who went to trouble for you.

Worth knowing

Three uses in one word. The thanks use implies “I troubled you”.