Definition:Concatenation (Formal Systems)

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

Concatenation is the process of placing elements of $\mathcal A$ next to each other to form a string.

For example, let $a, b, c \in \mathcal A$.

Then concatenating $b$ to $a$ results in the string $ab$, and concatenating $c$ gives the string $abc$. Concatenating $b$ then gives $abcb$.

Concatenating $aba$ to $aabcba$ gives the string $aabcbaaba$.

Linguistic Note
The word concatenation derives from the Latin word catena for chain. However, a string is not to be confused with a chain.