page_title: C-command
section_title: C-command and NPI Licensing
hierarchical_section_title: C-command / Applications / C-command and NPI Licensing
caption_attribution_description: English: Grammatical sentence with NPI
context_page_description: c-command is a relationship between the nodes of grammatical syntax trees. A working definition of c-command is that node X c-commands node Y if a mother of X dominates Y. C-command is closely associated with the generative phrase structure grammars of the Chomskyan tradition, and is not applicable to the tree structures of other theories of syntax, such as dependency grammars. C-command relations have served as the basis for many explorations and explanations of phenomena within the field of syntax. It has been taken to be the basic configurational relation underlying binding, and has played a central role in the analysis of diverse syntactic mechanisms, such as parasitic gaps and the scope of quantifiers.
  Informally, if a node has any sibling node, then it c-commands its siblings and all of their descendants; however, if a node doesn't have any siblings, then it c-commands everything that its parent c-commands.
context_section_description: Polarity items are lexical items (such as any, somewhat, or all) whose occurrence in the sentence is constrained to co-appearance with a licensing constituent (such as negation). C-command relations can be influential to the surface level structures of a sentence, as can be seen in Negative Polarity Item (NPI) Licensing. For example, in English, any can act as an NPI, therefore requiring a licenser such as negation. In order for the sentence containing an NPI to be grammatical, the licensor must c-command the NPI. Consider these sentences:
  Sentence 6: Lucy will not read any book.
  Sentence 7: *Anyone will not read a book.
  In the first sentence above, the licensor not c-commands the NPI any, resulting in a grammatical sentence. In reference to the tree at the left, the sister node of the Negative Phrase (acting as the licensor) is VP, which dominates the Determiner Phrase containing the NPI any; therefore, the licensor is c-commanding the NPI. Meanwhile, in the second sentence, the licensor does not c-command the NPI, as the NPI occurs above the licensor in the tree at the right. Therefore, since the licensor does not c-command the NPI, the sentence is ungrammatical.
caption: Tree illustrating c-command in grammatical sentence 6, NPI licensing
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