Definition:Formal Language/Also defined as

Formal Language: Also defined as

Some sources state that:

the alphabet $\AA$ must be a finite set for $\LL$ to be classified as a formal language

the formal language can consist of any arbitrary set of strings from $\AA$.

Examples

Empty Set forms Formal Language

The empty set $\O$ forms a formal language.

Set of Null Strings forms Formal Language

The set consisting of the null string $\epsilon$ forms a formal language.

Set of Palindromes over $\set {0, 1}$ forms Formal Language

The set of palindromes over $\set {0, 1}$ forms a formal language.

Also see

• Results about formal languages can be found here.

Sources

• 1979: John E. Hopcroft and Jeffrey D. Ullman: Introduction to Automata Theory, Languages, and Computation ... (previous) ... (next): Chapter $1$: Preliminaries: $1.1$ Strings, Alphabets and Languages