In generative grammar and related frameworks, a node in a parse tree c-commands its sister node and all of its sister's descendants. In these frameworks, c-command plays a central role in defining and constraining operations such as syntactic movement, binding, and scope. Tanya Reinhart introduced c-command in 1976 as a key component of her theory of anaphora. The term is short for "constituent command".
Definition and examples
Standard Definition Common terms to represent the relationships between nodes are below (refer to the tree on the right): M is a parent or mother to A and B. A and B are children or daughters of M. A and B are sisters or siblings. M is a grandparent or grandmother to C and D.Terms to represent the relationships between nodes is taken from Sportiche et al. (2014;2013, p. 24)
The standard 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. For a node (N1) to c-command another node (N2) the parent of N1 must establish dominance over N2.
Based upon this definition of dominance, node N1 c-commands node N2 if and only if:
Node N1 does not dominate N2, N2 does not dominate N1, and The first (i.e. lowest) branching node that dominates N1 also dominates N2.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).
For example, according to the standard 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 does not c-command any node because it does not have a sister node or any daughter nodes. 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 S. Kayne's theory of Antisymmetry.
Where c-command is used
Standard Definition A simplification of the standard definition on c-command is as follows:
A node A c-commands a node B iff Neither A nor B dominates the other, and Every branching node dominating A also dominates BThe standard definition is a simplification based on the many variations on c-command that can be found in pg. 616 in Barker (2012).
As such, we get sentences like: (1) [John] likes [her] Where [node A] John c-commands [node B]. This means that [node A] also c-commands [node C] and [node D], which means that John c-commands both [likes] and [her].
Syntax Tree In a parse tree (or syntax tree), nodes A and B are replaced with a DP constituent, where the DP [John] c-commands DP [he]. In a more complex sentence, such as (2), the pronoun could interact with its antecedent and be interpreted in two ways. (2) [John]i thinks that [he]i/m is smart In this example, two interpretations could be made: (i) John thinks that he is smart
(ii) John thinks that someone else is smart
In the first interpretation, [John] c-commands [he] and also co-references [he]. Co-reference is noted by the same subscript (i) present under both of the DP nodes. The second interpretation shows that [John] c-commands [he] but does not co-reference the DP [he]. Since co-reference is not possible, there are different subscripts under the DP [John] (i) and the DP [he] (m).
Definite Anaphora Example sentences like these shows the basic relationship of pronouns with its antecedent expression. However, looking at definite anaphora where pronouns takes a definite descriptions as its antecedent, we see that pronouns with name cannot co-refer with its antecedent within its domain.
(3) Hei thinks that Johni* is smart Where [he] c-commands [John] but [he]i cannot co-refer to [John]i*, and we can only interpret that someone else thinks that John is smart.
In response of the limits of c-command, Reinhart proposes a constraint on definite anaphora: A given pronoun [DP e.g., he in (3)] must be interpreted as non-coreferential with any distinct non-pronouns [e.g. John] in its c-command domain
Binding Theory The notion of c-command can be found in frameworks such as Binding Theory, which shows the syntactic relationship between pronouns and its antecedent.See Lasnik (1989) for more history on modern binding theory. The binding theory framework was first introduced by Chomsky in 1973 in relation to the treatment of various anaphoric phenomena, and has since been revised throughout the years. Chomsky's analysis places a constraint on the relationship between a pronoun and a variable antecedent. As such, a variable cannot be the antecedent of a pronoun to its left.
The first major revision to binding theory is found in Chomsky (1980) with their standard definitions: a. An anaphor α is bound in β if there is a category c-commanding it and coindexed with it in β b. Otherwise, α is free in βDefinitions taken from Lasnik (1989).
Quantificational Binding Compared to definite anaphora, quantificational expressions works differently and is more restrictive. As proposed by Reinhart in 1973, a quantificational expression must c-command any pronoun that it binds.Although Barker (2012) provides counterexamples to the c-command requirement in quantificational binding, he also mentions Reinhart's proposal and motivation for the need of c-command (3) [Every man] thinks that [he] is intelligent.Example sentence can be found on pg. 2 in Carminati, Frazier, & Rayner (2002). a. ∀x(man(x)): x thinks x is intelligent. (bound) b. ∀x(man(x)): x thinks y is intelligent. (coreferential or 'free')
In this example, the quantifier [every man] c-commands the other pronoun [he] and a bound variable reading is possible as the pronoun 'he' is bound by the universal quantifier 'every man'. The sentence in (3) show two possible readings as a result of the bounding of pronouns with the universal quantifier. The reading in (3a) states that for all man, they each think that they (he) are intelligent. Meanwhile, sentence (3b) state that for all men, they all think that someone (he) is intelligent. In general, for a pronoun to be bound by the quantifier and bound variable reading made possible, (i) the quantifier must c-command the pronoun and (ii) both the quantifier and pronoun have to occur in the same sentence.See Carminati, Frazier, & Rayner (2002) for more information on bound variables and c-command.
History Relative to the history of the concept of c-command, one can identify two stages: (i) analyses focused on applying c-command to solve specific problems relating to coreference and non-coreference; (ii) analyses which focused on c-command as a structural on a wide range of natural language phenomena that include but are not limited to tracking coreference and non-coreference.
Stage 1: Coreference The development of ‘c-command’ is introduced by the notion of coreference. This is denoted by the first stage of the concept of c-command.Jackendoff and Lasnik both explore the concept of c-command through the interactions found in coreferencing. See Lightfoot (1975) and Lasnik (1976). In the initial emergence of coreference, Jackendoff (1972).Jackendoff's pronominal coreference rule accounts for the pronoun and/or noun cycling that plays a key role in coreferencing. See Lightfoot (1975). officially states... If for any NP1 and NP2 in a sentence, there is no entry in the table NP2 + coref NP2, enter in the table NP1 - coref NP2 (OBLIGATORY)
In other words, this rule states that any noun phrases that have not been associated with a coreference rule, are assumed to be noncoreferential. The tree to the right specifies this through the cyclical leftward movement of the pronoun and/or noun.
This is, then, edited by Lasnik (1976)Lasnik's rule accounts for the concept of "precede-and-command" which hints at a potential dominance factor which is later explored in Stage 2. See Reinhart (1981:607). in which...
NP1 cannot be interpreted as coreferential with NP2 iff NP1 precedes and commands NP2 and NP2 is not a pronoun. If NP1 precedes and commands NP2, and NP2 is not a pronoun, then NP1 and NP1 are noncoreferential.According to this rule, it is essential that NP2 (denoted as NPy in the tree on the left) be a pronoun for the sentence to be grammatical, despite NP1 (denoted as NPx on the tree) being a pronoun or not. This can be shown through the examples below.
a) Lucy greets the customers she serves.
b) *She greets the customers Lucy serves.
c) *Lucy greets the customers Lucy serves.
d) She greets the customers she serves.
In this edition of coreference, Lasnik sets some restrictions on the permissible locations of NP1 and NP2, which hint at potential dominance.
Stage Two: Dominance This leads to Stage 2 of the concept of c-command in which particular dominance is thoroughly explored. The term 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.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. Reinhart (1976) states that...
A commands node B iff the branching node ⍺1 most immediately dominating A either dominates B or is immediately dominated by a node ⍺2 which dominates B, and ⍺2 is of the same category type as ⍺1
In other words, “⍺ c-commands β iff every branching node dominating ⍺ dominates β”
Chomsky adds a second layer to the previous edition of the c-command rule by introducing the requirement of maximal projections. He states...
⍺ c-commands β iff every maximal projection dominating ⍺ dominates β
This became known as "m-command."
The tree to the right compares the two definitions in this stage. Reinhart's "c-command" focuses on the branching nodes whereas Chomsky's "m-command" focuses on the maximal projections.Chomsky takes Reinhart's definition of c-command to formulate m-command. See Zhang (2016).
The current and widely used definition of c-command that Reinhart had developed was not new to syntax. Similar configurational notions had been circulating for more than a decade. In 1964, Klima defined a configurational relationship between nodes he labeled "in construction with". In addition, Langacker proposed a similar notion of "command" in 1969. Reinhart's definition has also shown close relations to Chomsky's 'superiority relation.'The 'superiority relation' denotes the superiority as asymmetrical where nodes A and B cannot be superior to each other. The difference between Reinhart's 'c-command' and Chomsky's 'superiority relation' is that sister nodes are permitted in the former whereas it is excluded in the latter. See Reinhart (1981:612).
Criticism and Alternatives Over the years, the validity and importance of c-command for the theory of syntax have been widely debated.Refer to Bruening's article in Language (2014) which provides debates on the validity of c-command. Linguists such as Benjamin Bruening have provided empirical data to prove that c-command is flawed and fails to predict whether or not pronouns are being used properly.C-command's failure to predict the proper usage of pronouns is discussed in Bruening's article in Language (2014).
Bruening's take on c-command