10.

Define senatorial courtesy. 

Senatorial courtesy is a long-standing unwritten, unofficial, and nonbinding political custom in the United States describing the tendency of U.S. senators to support a Senate colleague in opposing the appointment to federal office of a presidential nominee from that Senator's state. The practice is motivated by a general sense of collegiality among Senators and the assumption that a Senate colleague will have the best first-hand knowledge of the personal character and qualifications of nominees from his or her own state. It is also viewed as an 'important source of political patronage' for U.S. senators.