As per wikipedia: Cardinality refers to uniquess of data:
In SQL (Structured Query Language), the term cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column. Thus, a column with the lowest possible cardinality would have the same value for every row. SQL databases use cardinality to help determine the optimal query plan for a given query.
BUT, Oracle documentation explains it as: "The cardinality is the estimated number of rows that will be returned by each operation"
So, is this term has different meaning in SQL and in Oracle ? or i am missing something here ?