系安全带用英语怎么说？

系安全带用英语说作 "buckle up"，"fasten your seatbelt" 或 "put on your seatbelt"。它的来源可能源于汽车安全带的经典扣环形状，因此称之为 "buckle"。

例句：

Please buckle up before starting the car. 请开车前系好安全带。

Fasten your seatbelt, we're about to take off. 请系好安全带，我们即将起飞。

Put on your seatbelt, it's the law. 请系上安全带，这是法律规定。