* Graduate: This is a common and generally acceptable term, especially for diplomas from post-secondary institutions.
* Diploma holder: This is a straightforward and accurate description.
* Certified [Profession/Skill]: If the diploma certifies a specific profession or skill (e.g., a certified welder, a certified nursing assistant), then that specific title is most appropriate.
* [Specific Job Title]: The person might hold a job title that reflects their diploma, like "Registered Nurse" or "Project Manager".
In short, the best term depends on the *type* of diploma and the context in which you are using the term.