What is the difference between a Weak Entity and a Sub Entity?

Question :

What is the difference between a Weak Entity and a Sub Entity?

A Weak entity depends upon a regular entity for its existence whereas a Sub entity is part of a Regular entity. For example, an entity called Students is used to store all student details. Now, every student is enrolled for a course and there are some students who have taken a break from the course. In this kind of a scenario, we can have a Sub entity called Break-Students, which stores details of all students who have currently taken a break. Note that a Sub entity will contain all the columns of the super-entity from which it is derived. A Weak entity on the other hand has attributes that are different from those of the regular entity on which it is dependent.