An affinity diagram is a tool used to organize and group large amounts of data into meaningful categories or themes. There are several synonyms for this term, such as KJ method, affinity chart, or cluster analysis. The KJ method is named after its creator, Kawakita Jiro, and is often used in quality control processes. The affinity chart is a more visual representation of the data, with categories or themes written on sticky notes and organized on a chart. Cluster analysis is similar to the affinity diagram, but it uses statistical algorithms to group data based on similarities in characteristics. Overall, these synonyms all refer to the same process of organizing complex data into manageable categories.