A periodical is just a larger and more confusing word for journal. Technically, periodicals also include anything that is published on a regular schedule such as magazines. The vast majority of SBU's periodicals are journals, so the terms are virtually interchangeable.
Use the Contact links to the left to contact a librarian by phone, e-mail, or instant message. We're glad to help! In addition to the reference librarian who is on duty, you can also contact the library liaison for your academic area for help using resources related to your program.