User:Jshflynn/Definition:i-th letter

Definition
Let $\Sigma$ be an alphabet and let $x$ be a word over $\Sigma$.

Then the $i$-th letter of $x$ is the $i$-th term of $x$ when interpreted as a sequence over $\Sigma$.

It is denoted $x_i$.

Example
Example 1

Given the alphabet $\{$ a, 7, d, t, g $\}$ and the word $x = \langle$ g, t, d, g $\rangle$.

Then $x_2 =$ t.