In math, one says "let $G$ be a group", "let $A$ be an algebra", ...
For groups, the typical letters are $G$, $H$, $K$, ... For algebras, the typical letters are $A$, $B$, ...
I want to say things such as "let xxx be a conformal field theory"
and "let xxx $\subset$ xxx be a conformal inclusion".
Which letters should I use?
What is the usual way people go about this?
Here, I'm mostly thinking about chiral CFTs, but the question is also relevant for full (modular invariant) CFTs.