The term inertia in correspondence analysis is used by analogy with the definition in applied mathematics of "moment of inertia," which stands for the integral of mass times the squared distance to the centroid (e.g., Greenacre, 1984, p. 35). Inertia is defined as the total Pearson Chi-square for a two-way frequency table (e.g., as can also be computed in the Basic Statistics or Log-Linear methods of analysis) divided by the total sum of all observations in the table.

See also: Correspondence Analysis.