Definition 4.9.13.  Let u ∈ ℕ. We define:
Fldu := [Fld(Hom(A, B))A,B ∈ Fld(idC)C ∈ Fld(∘)D,E,F ∈ Fld]u is a/an u-small category
Remarks.

The objects of this category are actually isomorphism classes of fields.

References.