Define 'universal grammar (UG)’ and discuss principles and parameters with appropriate examples.

Universal Grammar (UG) is a theory in linguistics that suggests that the ability to acquire language is innate to humans and that all human languages share a common structural basis. This theory was proposed by Noam Chomsky in the 1950s. According to Chomsky, UG is the system of principles, conditions, and rules that are elements or properties of all human languages.

The Principles and Parameters theory, a part of UG, proposes that while there are certain grammatical principles that are universal and fixed, there are also parameters that can vary between languages.

Principles are the grammatical rules that are universal and apply to every language. For example, one principle is that in declarative sentences, the subject usually precedes the verb. This is true in many languages, such as English ("She runs"), Spanish ("Ella corre"), and French ("Elle court").

Parameters, on the other hand, are the points of variation between different languages. For example, the pro-drop parameter, which refers to whether or not subject pronouns can be dropped in a sentence, varies between languages. In English, which is a non-pro-drop language, you cannot drop the subject pronoun ("She runs" is correct, but "Runs" is not). However, in Spanish, which is a pro-drop language, you can drop the subject pronoun ("Corre" is as correct as "Ella corre").

In conclusion, Universal Grammar is a theory that suggests a common structural basis for all human languages, and the Principles and Parameters theory is a part of UG that explains the universal and variable aspects of different languages.