from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Equal in force, power, effectiveness, or significance.
  • adj. Logic Validly derived from each other; deducible.
  • adj. Equivalent.
  • n. An equivalent.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. having equal power or force
  • adj. able to be deduced from the other
  • adj. equivalent

from the GNU version of the Collaborative International Dictionary of English

  • adj. Having equal power or force; equivalent.
  • adj. Having equivalent signification and reach; expressing the same thing, but differently.

from The Century Dictionary and Cyclopedia

  • Having equal power or force; equivalent.
  • In logic, having the same meaning: applied to two propositions.
  • In mathematics, equal and parallel.


Middle English, from Old French, from Latin aequipollēns, aequipollent- : aequi-, equi- + pollēns, present participle of pollēre, to be powerful.
(American Heritage® Dictionary of the English Language, Fourth Edition)



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  • An equipollent system is kinda like an equivalent system except it doesn't adhere to the rigid body principle (the body has some flex mechanism or is not rigid).

    One of those words that don't seem like they really would exist but here it is anyways.

    October 2, 2008