Definition:Word (Formal Systems)

Let $$\mathcal{F}$$ be a formal language.

Let $$\mathcal{A}$$ be the alphabet of $$\mathcal{F}$$.

Then a word in $$\mathcal{A}$$ is defined as a finite string of symbols of $$\mathcal{A}$$.

Note
Not all words formed of symbols of $$\mathcal{A}$$ necessarily belong to $$\mathcal{F}$$.

Whether it does or not depends on the grammar of $$\mathcal{F}$$.

A word which does belong to $$\mathcal{F}$$ is sometimes called a well-formed word.