765 ILCS 120/3

For the purposes of this Act the word "owner" shall include not only the owner of fee simple title, but also the owner of any other interest in the land, including, without limitation, a contract purchaser, a lessee, and a life tenant. Provided, any conveyance shall bind only the interest of the grantor, nor shall any conveyance by a party having a limited interest be made if it violates the provisions of the instrument under which such grantor holds.