Tetradics transform dyadics in much the same way that dyadics transform vectors. They are represented using Hebrew characters and have 81 components (Morse and Feshbach 1953, pp. 72-73). The use of tetradics is archaic, since tensors perform the same function but are notationally simpler.
Tetradic
See also
Dyadic, Tetradic NumberExplore with Wolfram|Alpha
References
Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part 1. New York: McGraw-Hill, 1953.Referenced on Wolfram|Alpha
TetradicCite this as:
Weisstein, Eric W. "Tetradic." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Tetradic.html