Are tube amps class A ?

I understand transistor design but I'm a tube newbie... I've owned some CJ gear for 2 years now. When I think about amp classes it all comes down to bias current and switching. Are all tube amps essentially class A biased or is there still the concept of A/B ? I have an older tube design book somewhere but I'm thinking someone here will know.
You can bias a tube to operate class A, AB, B, or C just like a transistor.

Any amp you can build with an npn transistor has an equivalent that can be built with a tube. The big difference is there is no complementary device for a tube like you have with npn and pnp transistors.
Single-ended Triode amps are Class A by definition.
I have a CJ MV60 ... is it AB in ultralinear and A in triode or is it always AB?

It is a push-pull amp biased AB.

A push pull amp can be biased A, like VAC's 300B amps, but CJ is AB.