Principles and parameters
In UG principles and parameters can be defined as a framework in hunan brain and help the acquisition of the L1.According to UG a finite set of fundamental principles are common to all languages; e.g., that a sentence must always have a subject, even if it is not overtly pronounced. The principles are unchanging regardless of the actual language involved. These principles form part of the language faculty of the mind-UG.The claim is that it is impossible for a human mind to know a language without knowing these principles, since they are already present inside it.
UG explains the variation between languages through parameters.According to Chomsky a finite set of parameters determines syntactic variability amongst languages; e.g., a binary parameter that determines whether or not the subject of a sentence must be overtly pronounced. Languages can only vary within pre-set limits for a particular parameter.The parameter itself is universal but the values it may take vary from one language to another. For example any language a human being knows must ,among other things be either pro-drop or non-pro-drop.So,all languages must have a setting for each of the parameters affecting word order and must have one of possible settings for the governing category parameter of Binding Theory. The language knowledge of human minds takes the form of universal principles and variable parameters of ,whatever the language they have learnt.So,UG holds a set of principles and parameters arranged into modules such as Binding Theory and it is a computation system that ranges from the component of Phonological Form to the component of Logical Form ,that is ,from ’sound’ to ’meaning’.
As such, principles and parameters do not need to be learned by exposure to language. Rather, exposure to language merely triggers the parameters to adopt the correct setting.