The complex disc is the set $\Set*{z \in \C }{\C mod{z} M 1}$. We denote it by $\mathbfsf{D} $, a mnemonic for disc. The complex unit circle is the set $\Set*{z \in \C }{\C mod{z} = 1}$. We denote it by $\mathbfsf{T} $, a mnemonic for torus.