What is the process of distributing Senate seats after each census known as?

The process of distributing Senate seats after each census is known as reapportionment. This term specifically refers to the way in which seats in the Senate (and House of Representatives) are redistributed based on changes in population as determined by the decennial census.

Every ten years, when the census is conducted, it provides updated population data that federal and state governments use to determine how many congressional seats each state will receive. While the number of Senate seats per state remains fixed at two, reapportionment is more commonly associated with the House of Representatives, where the total number of seats (435) is distributed among the states based on their populations.

In contrast, redistricting is the process of drawing the district lines within a state to ensure that each district is roughly equal in population. Allocation generally refers to the distribution of resources or responsibilities among various entities, and constituency pertains to the group of voters or residents that an elected official represents. Therefore, reapportionment is the correct terminology for the process being discussed relating to the census and the distribution of congressional representation.