What is the correct terminology for 32-bit bits?

I am well versed in different architectures, providing 32-bit or 64-bit registers and how it all works at a low level. However, one thing always eluded me. Specific terminology as to whether 32 or 64 bit. For instance:

string XXX;

if (architecture == i386) XXX = "32"; else if (architecture == x86_64) XXX = "64";

... go on to use variable XXX ...

So what would I call my variable? Not architecture. Not a bit. Not "bus width" or "register width" (which seems completely out of place, I think)

So what would you call this variable and what would someone say in a conversation?