Adherence to (compliance with) drug treatment is important. However, only about half the people who leave a doctor's office with a prescription take the drug as directed. Among the many reasons people give for not adhering to drug treatment, forgetfulness is the most common.
Definition of periodical. 1  1 : periodic 1. 2  2a : published with a fixed interval between the issues or numbersb : published in, characteristic of, or connected with a periodical.
it is a publication usually between two to twelve pages in length it is issued weekly biweekly monthly quarterly or whenever necessary to serve the vital needs of the commercial or nonprofit group publishing it may have fewer than one hundred readers or as many as fifty thousand