A periodical publication, or just periodical, is a published work that appears in a new edition on a regular schedule. The most familiar examples are the newspaper, often published daily, or weekly; or the magazine, typically published weekly, monthly or as a quarterly. Other examples would be a newsletter, a literary journal or learned journal, or a yearbook.
These examples all are related to the idea of an indefinitely continuing cycle of production and publication: newspapers plan to continue publishing, not to stop after a predetermined number of editions. A novel, in contrast, might be published in monthly parts, a method revived after the success of The Pickwick Papers by Charles Dickens. This approach is called part-publication, particularly when each part is from a whole work, or a serial, for example in comic books or manga. It flourished in the middle of the nineteenth century, for example with Abraham John Valpy's Delphin Classics, and was not restricted to fiction.
Postal services often carry periodicals at a preferential rate; for example Second Class Mail in the United States only applies to publications issued at least thrice per year.