luckily

Compared meaning: luckily, in a lucky way (adverb).

比较义项：幸运地（副词）。

• fortunately

  Slightly more formal and neutral in tone; common in written or spoken narration, news reports, and formal speech to introduce a lucky turn of events.

  语气略正式、中性，常用于书面或正式口头叙述、新闻报道中，引出一个幸运的转折。

  Fortunately, the surgeon caught the problem during a routine checkup.

  幸运的是，外科医生在一次常规检查中发现了这个问题。

• luckily 本词

  More casual and conversational; common in everyday spoken English among friends or family to mention good luck in small, informal situations.

  语气更随意、口语化，常用于朋友或家人之间的日常对话，用来说一些小事上的运气好。

  Luckily, my roommate had an extra umbrella when it started pouring.

  幸运的是，开始下大雨时我室友正好多带了一把伞。

Fortunately and luckily are sentence adverbs meaning 'luckily', very close in meaning and often interchangeable. Luckily sounds more casual and everyday; fortunately sounds more formal, common in news reports or formal narration.

这两个词都用作句首或句中的语气副词，表示“幸运的是”，语气和用法非常接近，可以互换；但 luckily 略偏口语、随意，fortunately 略偏正式、书面，常见于新闻报道或较正式的叙述中。