User:Jshflynn/Definition:Alphabet
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Definition
Let $\Sigma$ be a non-empty finite set.
In the context of formal language theory $\Sigma$ is referred to as an alphabet.
Examples
Example 1
The set $\set {a, b, c}$ is an alphabet.
Example 2
The set $\set {\text{begin}, \text{end}, \text{while}, \text{do}, \text{if}, \text{then} }$ is an alphabet similar to ones used in programming languages.
Antiexamples
Antiexample 1
The set $\O$ fails to be an alphabet are required to be non-empty.