There are two types of disclaimers: statutory and terminal.
A U.S. patentee may give up (make disclaimer) all or part of the owner’s rights to enforce claims if done in writing and recorded in the USPTO (along with payment of the required fee). Such disclaimers are considered as part of the original patent, to the extent of the interest actually possessed by the disclaimant and by those claiming under him.
Any patentee or applicant may disclaim or dedicate to the public all or part of a patent’s enforceability term.