In Pentaho Data Catalog cardinality is a measure of the uniqueness of values within a table column concerning the total number of rows in that table. It helps understand the data's uniqueness and can assist in data analysis and profiling within Data Catalog.
Note: Cardinality calculation is particularly relevant for RDBMS data sources.
Once you've processed the data source within Data Catalog, go to Data Canvas and select a column. You can see the Cardinality score in the Statistics panel under the Summary tab.