拼写合适的单词补全句子（答案不区分大小写；单词提示中一根小短线代表一个字母）If you refer to the _____ of doing something, you are referring to a polite action.

根据句意，这里需要一个表示“礼貌行为”的单词。结合“refer to”结构，应填入“courtesy”，表示“礼貌、礼节”。完整句子为：
If you refer to the courtesy of doing something, you are referring to a polite action.

答案：courtesy