In an Enhanced Entity–Relationship (EER) diagram, which diagram shape represents an entity type?

Introduction / Context:
Recognizing the core ER/EER symbols accelerates both communication and correctness in data modeling. This question focuses on the symbol for the entity type itself.

Given Data / Assumptions:

• EER notation is a superset of classic ER symbols.
• Each symbol has a fixed, widely accepted meaning.

Concept / Approach:
The rectangle shape denotes an entity type. An entity type represents a set of real-world objects or concepts with shared properties. Ovals denote attributes and diamonds denote relationships; optionality and other constraints are indicated by markers and lines, not by replacing the rectangle.

Step-by-Step Solution:

Verification / Alternative check:
Any standard ERD legend confirms the mapping.

Why Other Options Are Wrong:

• Attribute → oval.
• Relationship → diamond.
• Optional One → not a shape; optional participation is indicated via constraints.

Common Pitfalls:
Mixing up relationship diamonds and entity rectangles when relationships are named with nouns; always check the shape, not the label alone.

Final Answer:
Entity