A more thorough explanation:

A determinable fee is a type of ownership interest in real property that is subject to a condition or limitation that, if violated, will result in the termination of the interest. This type of ownership interest is also known as a fee simple determinable or a base fee.

Example 1: John owns a piece of land that he has conveyed to the local school district for the purpose of building a new school. The conveyance is subject to the condition that the land must be used for educational purposes only. If the school district ever uses the land for any other purpose, John's ownership interest will automatically terminate and the land will revert back to him.

Example 2: Mary owns a house that she has conveyed to her son, Tom, with the condition that he must live in the house for at least five years. If Tom moves out of the house before the five-year period is up, Mary's ownership interest will automatically terminate and the house will revert back to her.

These examples illustrate how a determinable fee is subject to a condition or limitation that, if violated, will result in the termination of the ownership interest. In both examples, the ownership interest is contingent upon the satisfaction of a specific condition, and if that condition is not met, the interest will automatically terminate.