What interest does Owner A retain when giving a life estate to his sister?

When Owner A gives a life estate to his sister, he retains a reversionary interest. This means that after the life estate terminates—either upon the sister's death or when she no longer needs the property—the ownership automatically reverts back to Owner A or his heirs.

A life estate is a property interest that lasts for the duration of a specific person's life. Thus, while the sister enjoys the rights related to the property during her lifetime, Owner A still holds a stake in the property for the future. The reversionary interest is critical because it guarantees that Owner A will regain full ownership after the life estate ends, which is not the case for choices like remainder interest or joint tenancy interest. Remainder interest would involve transferring interests to another party after the life estate, which Owner A does not intend to do here, and joint tenancy interest refers to a different ownership structure altogether.