先是

In a sentence

• 先是他提到这个问题，然后我们展开了讨论。

  First, he mentioned this issue, and then we started discussing it.

  In this sentence, '先是' is used to indicate the first action or element in a series of events.

• 她的早餐先是面包，无聊的时候会选择煎蛋。

  Her breakfast is first bread, and sometimes she chooses fried eggs when she feels bored.

  Here, '先是' shows the primary preference or initial choice when describing habits.

• 会议上先是介绍了最新的技术，然后我们进行了产品演示。

  During the meeting, the latest technology was introduced first, followed by our product demonstration.

  In this context, '先是' highlights the order of events occurring in a formal situation.