Implicational hierarchy

Implicational hierarchy, in linguistics, is a chain of implicational universals. A set of chained universals is schematically shown as in (1):

(1) A < B < C < D

It can be reformulated in the following way: If a language has property D, then it also has properties A, B, and C; if a language has a property C, then it also has properties A and B, etc. In other words, the implicational hierarchy defines the possible combinations of properties A, B, C, and D as listed in matrix (2):

A B C D
Type 1: + + + +
Type 2: + + + -
Type 3: + + - -
Type 4: + - - -
Type 5: - - - -

Implicational hierarchies are a useful tool in capturing linguistic generalizations pertaining the different components of the language. They are found in all subfields of grammar.