What types of relationships exist in a class diagram?

In UML class diagram structures, the main types of relationships between classes include:

• Association — a simple connection between objects, indicating that one class uses or is related to another. It can be unidirectional or bidirectional.
• Aggregation — a special type of association representing a "part-whole" relationship, where the part can exist independently of the whole.
• Composition — a stricter form of aggregation where the part cannot exist without the whole (hard dependency).
• Inheritance (Generalization) — an "is-a" relationship where a subclass inherits properties and behaviors from a superclass.
• Dependency — a temporary relationship where one class uses another, for example, in method parameters.

Example:

Class Car --(composition)--> Class Engine
Class Car --(association)--> Class Driver
Class SportsCar --(inheritance)--> Class Car