c-command (constituent command) is a relationship between the nodes of grammatical parse trees. It is closely associated with the phrase structure grammars of the Chomskyan tradition (Government and Binding, Minimalist Program), and may not be valid or applicable to the tree structures of other theories of syntax, such as dependency grammars. The relation of c-command has served as the basis for many explorations and explanations of phenomena 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 speaking, a node in a tree c-commands its sibling node(s) and all of its siblings' descendants; however, a node without siblings c-commands everything that its parent c-commands.
Definition and example
The definition of c-command is based partly on the relationship of dominance: Node N1 dominates node N2 if N1 is above N2 in the tree and one can trace a path from N1 to N2 moving only downwards in the tree (never upwards); that is, if N1 is a parent, grandparent, etc. of N2.
Based upon this definition of dominance, node A c-commands node B if and only if:
For example, according to this definition, in the tree at the right,
- M does not c-command any node because it dominates all other nodes.
- A c-commands B, C, D, E, F, and G.
- B c-commands A.
- C c-commands D, F, and G.
- D c-commands C and E.
- E c-commands D, F, and G.
- F c-commands G.
- G c-commands F.
If node A c-commands node B, and B also c-commands A, it can be said that A symmetrically c-commands B. If A c-commands B but B does not c-command A, then A asymmetrically c-commands B. The notion of asymmetric c-command plays a major role in Richard Kayne's theory of Antisymmetry.
The term itself, i.e. c-command, was introduced by Tanya Reinhart in her 1976 dissertation, and is a shortened form of constituent command. Reinhart thanks Nick Clements for suggesting both the term and its abbreviation. The concept Reinhart was developing was, however, not new to syntax. Similar configurational notions had been circulating for more than a decade. In 1963 Klima and Lees proposed a configurational relationship between nodes expressed as "in construction with", and Langacker proposed the notion of "command" in 1969.
One application of the c-command relation is found in the study of binding, where the possible syntactic relationships between personal pronouns and their antecedents are studied. These relationships appear to be subject to certain restrictions; it was hypothesized that one such restriction is that the pronoun cannot appear in a position where it c-commands its antecedent. Consider the sentences:
- He said that John was coming.
- His mother said that John was coming.
In the second sentence, his and John may co-refer ("his mother" may mean John's mother). In the first sentence, however, "he" cannot refer to John. This was explained, at least in the original binding theory, by the fact that he c-commands John in the first sentence, whereas his does not c-command John in the second.
Criticism and alternatives
The validity and importance of c-command for the theory of syntax is a debated issue. In most cases, c-command correlates positively with precedence (linear order), that is, when node A c-commands node B, it is usually the case that node A also precedes node B. Furthermore, basic S(V)O (subject-verb-object) word order in English correlates positively with a hierarchy of syntactic functions, subjects outranking objects. Subjects typically precede objects in declarative sentences in English and related languages. These two insights suggest that theories of syntax that build on c-command have misconstrued the importance of precedence and/or the hierarchy of syntactic functions. What c-command is intended to address is arguably more accurately analyzed in terms of precedence and the syntactic functions. Further, the c-command concept was developed primarily with its ability to address syntactic phenomena of English, a language with relatively strict word order. When confronted with the much freer word order of many other languages, the insights provided by c-command are less compelling, since linear order becomes less important.
As just suggested, the phenomena that c-command is intended to address may be more plausibly examined in terms of linear order and a hierarchy of syntactic functions. Concerning the latter, some theories of syntax take a hierarchy of syntactic functions to be primitive. This is true of Head-Driven Phrase Structure Grammar (HPSG), Lexical Functional Grammar (LFG), and dependency grammars (DGs). The hierarchy of syntactic functions that these frameworks posit is usually something like the following: SUBJECT > FIRST OBJECT > SECOND OBJECT > OBLIQUE OBJECT. Numerous mechanisms of syntax are then addressed in terms of this hierarchy.
- Most syntax textbooks on generative grammar acknowledge, define, and build on the c-command concept. See for instance Radford (2004:75ff) and Carnie (2013:127ff.).
- The definition of c-command given here is taken from Haegeman (1994:147). The same or similar definitions of c-command can be found in numerous textbooks on syntax, e.g. Radford (2004:75) and Carnie (2013:127).
- Carnie (2002:57) mentions this point, i.e. that Reinhart thanked Clements for suggesting the term c-command. The term c-command may also have been chosen so as to contrast with the similar notion kommand (often read as "k-command"), proposed by Lasnik (1976). See Keshet (2004) in this regard.
- The notion "in construction with" appeared in Klima and Lees' article in the journal Language (1963), and Langacker's notion of "command" appeared in an article in the journal Modern Studies of English (1969).
- See for instance Bruening's article in Language (2014). This article challenges the validity of c-command on more than one front.
- HPSG addresses the c-command effects in terms of o-command (obliqueness command). The syntactic functions are ranked in terms of their level of "obliqueness", subjects being the least oblique of all the functions. See Pollard and Sag (1994:248) and Levine and Hukari (2006:278f.).
- LFG addresses the c-command effects in terms of a straightforward ranking of syntactic functions associated with f-structure (functional structure). See Bresnan (2001:198).
- Concerning DGs emphasis on the importance of syntactic functions, see for instance Mel'c̆uk (1988:22, 69).
- Bresnan, J. 2001. Lexical Functional Syntax. Blackwell.
- Bruening, B. 2014. Precede-and-command revisited. Language 90(1).
- Carnie, A. 2002. Syntax: A generative introduction, 1st edition. Oxford: Blackwell Publishing.
- Carnie, A. 2013. Syntax: A generative introduction, 3rd edition. Malden, MA: Blackwell Publishing.
- Haegeman, 1994. Introduction to Government and Binding Theory, 2nd edition. Oxford: Blackwell Publishing.
- Kayne, R. 1994. The antisymmetry of syntax. Linguistic Inquiry Monograph Twenty-Five. MIT Press.
- Keshet, E. (2004-05-20). "24.952 Syntax Squib". MIT.
- Klima, E. and R. Lees. 1963. Rules for English pronominalization. Language 13, 17-28.
- Lasnik, Howard. 1976. Remarks on coreference. Linguistic Analysis 2, 1-22.
- Levine, R. and T. Hukari 2006. The unity of unbounded dependency constructions. Stanford, CA: CSLI Publications.
- Pollard, C. and I. Sag. 1994. Head-driven phrase structure grammar. Chicago: University of Chicago Press.
- Radford, A. 2004. English syntax: An introduction. Cambridge, UK: Cambridge University Press.
- Reinhart, T. 1976. The syntactic domain of anaphora. Doctoral dissertation, Massachusetts Institute of Technology. (Available online at http://dspace.mit.edu/handle/1721.1/16400).
- Reinhart, T. 1983. Anaphora and semantic interpretation. London: Croom Helm.
- c-command and pronouns
- Node relations, University of Pennsylvania
- Some Basic Concepts in Government and Binding Theory