1. a process in which a complex item is separated into its simpler constituent elements. For example, in problem solving, it is a strategy in which a problem is transformed into two or more simpler problems.

2. in statistics, the breaking down of total effects or parameters into their different aspects. For example, in an analysis of variance, one may break down the total variance into the portion that concerns how the means vary between groups and the portion that concerns how much random variance there is within each group. If the between-group variance is significantly larger than the within-group variance, there is some evidence for a difference in means across groups.