Each L-function $L$ has a label of the form d-N-q.k-x-y-i, where

- $d$ is the degree of $L$.
- $N$ is the conductor of $L$. When $N$ is a perfect power $m^n$ we write $N$ as $m$e$n$, since $N$ can be very large for some imprimitive L-functions.
- q.k is the label of the primitive Dirichlet character from which the central character is induced.
- x-y is the spectral label encoding the $\mu_j$ and $\nu_j$ in the analytically normalized functional equation.
- i is a non-negative integer disambiguating between L-functions that would otherwise have the same label.