A more thorough explanation:

Ademption by extinction is a legal term that means when someone leaves property to someone else in their will, but that property is no longer available when the will takes effect. This means that the person who was supposed to receive the property will not get it.

For example, if a father leaves his car to his son in his will, but he sells the car before he dies, the son will not get the car because it is no longer available. The gift of the car has been adeemed by extinction.

It is important to note that the person who was supposed to receive the property will not get anything else in its place. In the example above, the son will not get any money from the sale of the car.

There are some cases where it is not clear whether ademption by extinction has occurred. For example, if a mother leaves her son 100 shares of a certain stock in her will, but she sells those shares and buys 100 shares of a different stock before she dies, it is unclear whether the son will still receive the shares. Some courts have held that this is not ademption by extinction because the mother's intention was still to leave her son 100 shares of stock, even if it was a different type of stock.

Overall, ademption by extinction can be a complicated legal issue, but it is important to understand if you are creating or inheriting a will.