class
mathematical collection of sets that can be defined based on a property of its members (set theory)
subclass
class whose elements are all elements of a given other class
theory
set of formula that can be deduced from axioms in some given logic
Class of groups
Collection of groups
universe
in set theory, a set large enough such that most ordinary mathematical constructions can take place within it
modality
way to class a proposition in logic, like necessarily true, possibly true, impossible ...
set
well-defined mathematical collection of distinct objects
pitch class
set of musical pitches modulo the octave
category
class of sets
elementary class
class consisting of all structures satisfying a fixed first-order theory
index set
classes of partial recursive functions, specifically they give all indices of functions in that class according to a fixed enumeration of partial recursive functions
equivalence partitioning
software testing technique