Projection principle

In linguistics, the projection principle is a stipulation proposed by Noam Chomsky as part of the phrase structure component of generative-transformational grammar.

Under the projection principle, the properties of lexical items must be preserved while generating the phrase structure of a sentence.

The Projection Principle requires that reference to these categories surfaces at every level of a syntactic phrase structure.

All three of these levels are seen because the projection principle requires that the category of John, Noun, be represented throughout the structure.

The verb run has an obligatory argument, its subject (a DP agent), which must appear in the sentence.

These were hypothesized to enter the slots in pre-generated structures waiting to be filled by the lexical material.

The projection principle therefore obviates the need for phrase structure rules in the generative component.

But the linearity in which complements, specifiers and adjuncts attach can be changed based on the language.

This is especially noticeable when a DP raises to Spec TP through the Extended Projection Principle (EPP).

The Extended Projection Principle (EPP) refers to the highest Tense Phrase containing a subject.

Once all of the projection principles of LOS are satisfied, EPP is activated when there is movement from one part of the tree to another.

In order to satisfy the EPP we must move the DP John into spec TP, to allow for the TP subject to be filled[6] By moving the DP we are altering the sentence making it John will Run.