Pē'ri-ŏd'ic or Pē'ri-ŏd'ic-al1, a.
a. [Fr. périodique, It. & Sp. periodico, Lat. periodicus, Gr. περιοδικός.]
Sense 1. Performed in a circuit, or in a regular revolution in a certain time, or in a series of successive circuits: as, the periodical motion of the planets round the sun; the periodical motion of the moon round the earth.
Sense 2. Happening, by revolution, at a stated time; returning regularly, after a certain period of time; acting, happening, or appearing, at fixed intervals; recurring.
Sense 3. (Rhet.) Pertaining to a period; constituting a complete sentence.