Real Dictionary

courtesy
Courtesies are polite, conventional things that people say in formal situations.
singular noun: If you refer to the courtesy of doing something, you are referring to a polite action.
uncountable noun: Courtesy is politeness, respect, and consideration for others.

courtesy in American English
courteous behavior; gracious politeness
adjective: done or performed as a matter of courtesy or protocol
noun: excellence of manners or social conduct; polite behavior