Entropy
In physics, the word entropy has important physical implications as the amount of ``disorder'' of a system. In mathematics, amore abstract definition is used. The (Shannon) entropy of a variable 
is defined as
where
is the probability that is in the state 
, and 
is defined as 0 if 
. The joint entropy ofvariables 
, ..., 
is then defined by
See also Kolmogorov Entropy, Kolmogorov-Sinai Entropy, Maximum Entropy Method, Metric Entropy,Ornstein's Theorem, Redundancy, Shannon Entropy, Topological Entropy
References
Ott, E. ``Entropies.'' §4.5 in Chaos in Dynamical Systems. New York: Cambridge University Press, pp. 138-144, 1993.
- Sierpinski Sieve
- Sierpinski Sponge
- Sierpinski's Prime Sequence Theorem
- Sierpinski's Theorem
- Sierpinski Tetrahedron
- Sierpinski Triangle
- Sieve
- Sieve of Eratosthenes
- Sievert Integral
- Sievert's Surface
- Sifting Property
- Sigma Algebra
- Sigma Function
- Sigmoid Curve
- Sigmoid Function
- Sign
- Signalizer Functor Theorem
- Signature (Knot)
- Signature (Quadratic Form)
- Signature (Recurrence Relation)
- Signature Sequence
- Signed Deviation
- Significance
- Significance Test
- Significant Digits