Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now

# Tag Info

$\Sigma$ is the alphabet of the grammar and so $\Sigma^k$ is the set of words of length $k$ from that alphabet. Finally $L\cap\Sigma^k$ is then the set of such words that are in $L$, i.e., that are generated by the grammar. (This should probably be clarified in the Wikipedia entry in some fashion.)