See also: impédance




impede +‎ -ance. Coined by Oliver Heaviside in 1886.


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impedance ‎(countable and uncountable, plural impedances)

  1. (physics) A measure of the opposition to the flow of an alternating current in a circuit; the aggregation of its resistance, and inductive and capacitive reactances; the ratio of voltage to current treated as complex quantities.
  2. (physics) A quantity analogous to electrical impedance in some other energy domain
    1. (physics, usually with “mechanical”) a measure of opposition to motion of something subjected to a force; the ratio of force to velocity treated as complex quantities.
    2. (physics, usually with “acoustic” or “sound”) the ratio of sound pressure to volume flow rate treated as complex quantities.
  3. (by analogy, software engineering, usually with “mismatch”) a measure of the opposition caused by differences between two paradigms, especially between object-oriented development and relational databases
    • 1997, Bhavani M. Thuraisingham, Data Management Systems: Evolution and Interoperation (ISBN 0849394937), CRC Press, page 33:
      Some argue that having impedance mismatch is difficult for programming intensive applications.
    • 2002, Jim Melton, Advanced SQL:1999: Understanding Object-Relational and Other Advanced Features (ISBN 1558606777), Morgan Kaufmann, page 353:
      But the impedance mismatch between SQL and Java was no better than between SQL and other languages.
    • 2004, Scott W. Ambler, The Object Primer: Agile Model-Driven Development with UML 2.0 (ISBN 1397805218), Cambridge University Press, page 442:
      Why does a technological impedance mismatch exist?

Usage notesEdit

Impedance is universally given the symbol Z in technical works which is often used as a synonym for the word even in running text.

Derived termsEdit

Related termsEdit