A more thorough explanation:

Definition: Subject to open, also known as subject to partial divestment, is a type of estate where the property is given to a specific group of people, such as a person's children. However, the group is not fully defined and can include additional individuals in the future.

Example: John creates a trust for his children, subject to open. At the time of creating the trust, John has two children, Tom and Sarah. The trust specifies that the property will be divided equally between them. However, the trust also allows for any additional children John may have in the future to be included in the distribution of the property.

This means that if John has another child, say, Emily, she will also be entitled to a share of the property. The class of beneficiaries is open to include any future children John may have.

Another example: A university creates a scholarship fund for students who are studying science. The scholarship is subject to open, meaning that the university can add additional criteria for eligibility in the future. For example, the university may decide to include students who are studying engineering or technology in the future.

This means that the class of eligible students is not fully defined and can be expanded to include additional criteria in the future.