This is the 10125th most frequent Japanese word.
酒井
"Sakai" is a Japanese surname.
Here, "酒井" is used as a surname for addressing a particular individual.
酒井さんは私の友達です。
Mr./Ms. Sakai is my friend.
In this context, "酒井" is part of the name of a liquor store, marking ownership or naming convention.
私たちは昨日酒井酒店へ行きました。
We went to Sakai Liquor Store yesterday.
Here, "酒井" identifies the name of a factory, signifying a location or establishment.