A more thorough explanation:

Definition: En mort mayne (en mort mayn) is a French term that means "in dead hand." It refers to the condition of lands or tenements that are held in perpetuity by an ecclesiastical or other corporation. This is also known as mortmain.

Examples: If a church owns a piece of land and it is held in mortmain, it means that the church will always own that land and it cannot be sold or transferred to anyone else. This is because a corporation, like a church, does not die and therefore the land will never escheat or pass by inheritance. This also means that no inheritance taxes will ever be paid on the land.

Explanation: The examples illustrate how en mort mayne or mortmain works in practice. When a piece of land is held in mortmain, it is owned by a corporation that will never die. This means that the land cannot be sold or transferred to anyone else, and it will never pass by inheritance. This is important because it ensures that the land remains in the hands of the corporation, such as a church, for perpetuity.