3.6.2.1 Cardinality and Optionality
The maximum degree is called cardinality and the minimum degree is called optionality. In another context the terms 'degree' and 'cardinality' have different meanings. In [Date 4th ed. p240] 'degree' is the term used to denote the number of attributes in a relation while `cardinality' is the number of tuples in a relation. Here, we are not talking about relations (database tables) but relationship types, the associations between database tables and the real world entity types they model.