different between retardance vs retardation

English

Etymology

From Middle French retardance

Noun

retardance (countable and uncountable, plural retardances)

1. (physics) The difference in phase shift between two characteristic polarizations of light upon reflection from an interface. Retardance can be reported in the Abelès or Mueller conventions. The retardance phase shift angle is often specified in degrees.

English

Etymology

retard +? -ation

Noun

retardation (countable and uncountable, plural retardations)

1. The act of retarding or delaying; hindrance.
   1. (acoustics) The distance by which one wave is behind another.
   2. (music) The act of diminishing the rate of speed.
   3. (telegraphy) A decrease in the speed of telegraph signalling.
2. The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
3. (colloquial, derogatory, offensive) Extreme stupidity.
4. That which retards; an obstacle; an obstruction.
5. (physics) Deceleration; reduction in the magnitude of velocity.
6. (music) A suspension which resolves upwards.

Related terms

References

• retardation in The Century Dictionary, New York, N.Y.: The Century Co., 1911.
• retardation in Webster’s Revised Unabridged Dictionary, G. & C. Merriam, 1913.