Theory that accounts for similarities and differences of natural languages.

According to the Principles & Parameters approach, all languages share a "core set" of principles and constraints. In addition to that, it is posited that all languages also have set of binary parameters, that can be set on or off, thus determining the particular structures of different languages. For example, the head directionality parameter is a proposed parameter that classifies word order accordingly to the placement of the head stem, which can be either:

  • Head-final (or head-last): Heads follow phrases in forming larger phrases
  • Head-initial (or head-first): Heads precede phrases in forming larger phrases