Definition:String

Definition
Let $\mathcal A$ be an alphabet of symbols.

A string (in $\mathcal A$) is a sequence of symbols from $\mathcal A$.

There is no limit to the number of times a particular symbol may appear in a given string.

Also defined as
Some sources use the word string to mean a finite string, that is, what is defined on as a word.

Also see

 * Definition:Substring
 * Definition:Initial Part
 * Definition:Null String
 * Definition:Word (Formal Systems)
 * Definition:Concatenation (Formal Systems)