Final answer:
A weak entity is an entity whose identifier includes the identifier of another entity, while a strong entity is an entity that can exist independently and has a unique identifier of its own.
Step-by-step explanation:
A **weak entity** is an entity whose identifier includes the identifier of another entity. It depends on the existence of the other entity for its own existence. In the context of databases, a weak entity is often associated with a **strong entity** through a **identifying relationship**.
For example, let's consider a database for a library. The **Book** entity may have a **Book Copy** entity as a weak entity. The identifier of a book copy includes the identifier of the book it belongs to. In this case, the **Book Copy** entity would be considered a weak entity.
On the other hand, a strong entity is an entity that can exist independently and has a unique identifier of its own. It doesn't rely on other entities for its existence. In the library database example, the **Book** entity can exist on its own and has its own identifier, making it a strong entity.