1. Relative to a period or periods.
  2. Having repeated cycles.
  3. Occurring at regular intervals.
  4. periodical
  5. Pertaining to the revolution of a celestial object in its orbit.
  6. for which any return to it must occur in multiples of <math>k</math> time steps, for some <math>k>1</math>.
  7. Having a structure characterized by periodic sentences.
  8. Relating to, derived from, or designating, the highest oxygen acid (HIO) of iodine.

Adjective (etymology 2)

  1. Of or derived from a periodic acid.

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