Entities can be thought of as the nouns that represent items in the accounting system. Employees, customers, vendors, and inventory items are examples of entities. ER diagrams identify the entities, which become the records in a database, and the attributes of entities that become the fields of those records.
The relationships between entities in ER diagrams are depicted by a concept called cardinality. Cardinality refers to how many instances of an entity relate to each instance of anot 
her entity.
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