Unfortunately; used to express regret or to say that circumstances are not favorable.
あいにく今日は都合が悪くて参加できません。
Unfortunately I can't attend today; it's not convenient.
あいにく雨が降ってきたのでピクニックは中止になった。
Unfortunately it started to rain, so the picnic was canceled.
あいにくその商品は在庫切れです。申し訳ありません。
Unfortunately that item is out of stock. I'm sorry.