核心问题
（1）The plane was late and detectives were waiting at the airport all morning. (NCE,2,L.7,外研社,p.36)
(2) When the plane arrived, some of the detectives were waiting inside the main building while others were waiting on the airfield. (NCE, 2, L. 7, 外研社, p. 36)
该书在课文注释中说：“at the airport，在机场上。和下文中的 on the airfield 是同义词组。”
请问 at the airport 与 on the airfield 是同义词组吗？
词典解答
虽然 airport 与 airfield 都汉译为“机场”，但它们所指的内容并不相同：airfield 只是指飞机升降和停放的地方，而 airport 除此之外，还包括候机大楼。因此，它们所表示的概念并不相同，即后者概念的外延比前者大。因此，句(1)中的 at the airport 是不能用 on the airfield 来替换的。