A car's ignition switch serves several purposes. First, it allows you to control the power to many of the car's accessories, preventing accessories from running down the car's battery when the car is parked for a long period of time.
Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation. In the common data architecture, cardinality is documented with data integrity but not with data structure. There are several types of cardinality defining relationships between occurrences of entities on two sides of the line of relationships.
Vertex Cardinality. The number of vertices, the cardinality of V, is called the order of graph and devoted by |V|. We usually use n to denote the order of G. The number of edges, the cardinality of E, is called the size of graph and denoted by |E|. We usually use m to denote the size of G.