The term **information** covers signs, signals and messages with their syntactic, semantic and pragmatic aspects.

Uncertainty (and thus information content) of a random event *i* may be quantitatively described in form of the negative logarithm of its probability with

*I* = - ld *p*_{i}

where ld denotes the dual logarithm as ld *M* = lg *M* / lg 2 = ln *M* / ln 2

The quantity of an information stream produced by an ergodic source is given with Shannon's equation as

*H* = - *K* Sigma _{i = 1} ^{n} (*p*_{i} ld *p*_{i}).

*H* is referred to as the entropy of the information source.

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