Learn in the textbookClassifying Data by Attribute and Structure
DefinitionCross-section data (クロスセクションデータ) takes a slice at one point in time and gathers many subjects side by side.
ExplanationExamples include each store's sales in the same month or each region's population in a given year, and it suits comparing subjects with one another. In the table above, reading one column (a month) down gives cross-section data, and reading one row (a store) across gives time-series data.
AnalogyLike a class photo taken one morning. You can compare everyone at that moment, but nothing about how they change afterward appears in it.
Memory hook"Cross section" means a slice. Picture one cut taken straight across the flow of time.