pentads

Noun

pentad (plural pentads)

1. Synonym of quinquennium: a five-year period, especially in reference to the first and second halves of calendrical decades.

   Synonyms:

   quinquennium

2. A five-day period, especially a temperature average taken every five days.
3. A five-day division of the Chinese calendar, forming part of a solar term (Chinese: 候).
4. A pentavalent element or group: an atom or molecule with a valence of five, comparable with five atoms of hydrogen.
   • Nitrogen is a pentad in the ammonium compounds.