Attendance at Friday's training workshop is voluntary, but managers strongly recommend it.

週五的培訓工作坊採自由參加，但主管們強烈建議出席。

The airline offered vouchers to passengers who took voluntary seat changes on the overbooked flight.

航空公司提供兌換券給在超賣航班上自願更換座位的旅客。

Several employees accepted the voluntary retirement package announced in last week's email.

有好幾位員工接受了上週電子郵件中宣布的自願退休方案。