noun
A number believed to bring good luck, often used in contexts like lotteries, sports, or personal superstitions.
彼のラッキーナンバーは7だ。
His lucky number is 7.
宝くじを買うときは、いつもラッキーナンバーを選ぶ。
When I buy a lottery ticket, I always choose my lucky numbers.
Borrowed from English 'lucky number'.