Seniority
Seniority is the concept of a person or group of people taking precedence over another person or group because the former is either older than the latter or has occupied a particular position longer than the latter. Seniority is present between parents and children and may be present in other common relationships, such as among siblings of different ages or between workers and their managers.
Under a seniority system, control is often granted to senior persons due to length of service in a given position. When persons of senior rank have less length of service than their subordinates, "seniority" may apply to either concept.
In armed forces
In some military command structures, the length of time someone has held a particular rank is called "seniority in grade" and determines whether that person is senior to another person of the same rank. For instance, a captain who was promoted five years ago can give orders to a captain who was promoted three years ago.
In politics
Seniority in United States politics, when used out of context, is informally defined as the number of years one member of a group has been a part of the group. For example, as of January 2015, John Conyers from Michigan is the most senior member of the House of Representatives. However, "seniority" can also refer to political power attained by position within the United States Government. For further details, see: