numeric or continuous: integer (# of children in fam) and real (decimal)  categorical nominal or polynomial: categorical data types (variables treated as symbols or names), unordered, ordered
numeric or continuous: integer or real categorical or nominal or polynominal: ordered or unordered
discrete { ordered {ordinal, quantitative}, undordered{nominal, categories} continuous{ ordered {fields {altitude, temperature}}, unordered { cyclic values eg directions, hues}