adj of or pertaining to a period; constituting a complete sentence.
2. periodical ·adj of or pertaining to a period or periods, or to division by periods.
3. periodical ·noun a magazine or other publication which appears at stated or regular intervals.
4. periodical ·adj performed in a period, or regular revolution; proceeding in a series of successive circuits; as, the periodical motion of the planets round the sun.
5. periodical ·adj happening, by revolution, at a stated time; returning regularly, after a certain period of time; acting, happening, or appearing, at fixed intervals; recurring; as, periodical epidemics.