Sumimasen is a versatile phrase meaning "Excuse me" or "I am sorry." You use it to apologize for minor offenses, to get someone's attention (like in a shop), or to express thanks for a small favor that might have inconvenienced someone. For example, "すみません、この電車は渋谷に行きますか？" (Excuse me, does this train go to Shibuya?).

「すみません」は、謝る時、人に呼びかける時、軽い感謝の時に使います。「すみません、ちょっといいですか？」