unfortunately; used to convey regrettable or disappointing information (similar to 'I'm sorry to say' or 'regrettably').
残念ながら、来週の打ち合わせは中止になりました。
Unfortunately, next week's meeting has been canceled.
残念ながらその商品は現在在庫がありません。
Unfortunately, that product is currently out of stock.
残念ながら彼女は今日のイベントに参加できないそうです。
Regrettably, she won't be able to attend today's event.