Applicant

inventor or joint inventors who are applying for a patent on their own invention, or the person mentioned in 37 CFR 1.42, 1.43 or 1.47 who is applying for a patent in place of the inventor.

-- see 37 CFR 1.41 and MPEP 605

A person who is applying for a patent. In the U.S., the applicant must be the inventor, except in exceptional circumstances. One or more than one person can apply for a patent. In jurisdictions other than the U.S., any legal "person" (e.g., individual or corporation) may be an applicant for a patent. MPEP 605.

The subscriber is sometimes called an applicant after applying to a certification authority for a certificate, but before the certificate issuance procedure is completed.