Final answer:
The practice that awards committee leadership to the longest-serving member of the majority party is known as the Seniority system, which plays a significant role in the organization and hierarchy of the U.S. Congress.
Step-by-step explanation:
The term used to describe the practice that gives the member of the majority party with the longest continuous service on a committee the leadership of that committee is the Seniority system. This practice is part of the organizational structure of both the House and the Senate in the U.S. Congress. According to seniority, those with longer tenures in Congress (and consequently, in their respective committees) are given priority for chair positions. This system influences various aspects of legislative work, including the assignment of office space and the hierarchy of seating on the chamber floors.
In the context of the legislative process, this practice illustrates an authority that emanates from long-standing custom. The seniority system helps to maintain order and stability within the committee framework, ensuring that experienced legislators lead in areas where they supposedly have developed expertise. However, it should be noted that this system is not a formally inscribed rule but rather a conventional practice that has persisted over time.