# C-command

In syntax, C-command is a binary relation between nodes in a tree structure which is defined as follows:

``` (i) Node A c-commands node B iff
```
```    a  A =/= B,
b  A does not dominate B and B does not dominate A, and
c  every X that dominates A also dominates B.
```
``` (ii)
X2
/ \
A  X1
/ \
B  C
```

In (ii) A c-commands B since A =/= B (cf. (i)a), A does not dominate B, nor does B dominate A (cf. (i)b); and the node which dominates A, X2, also dominates B (cf. (i)c). X1 in (ii) is not relevant to (i)c: although it dominates B, it does not dominate A.

For the possible choices of X in (i)c several options have been proposed. The first option is to interpret X as any branching node. Under this interpretation A c-commands B iff (ia) and (ib) are met and the first branching node dominating A also dominates B. This structural relation is sometimes referred to as strict c-command.

An alternative option for the possible values of X in (i)c is to count only maximal projections. Under this interpretation A is said to m-command B.

### Examples

In (iii) V c-commands NP the book, but not the PP in the store: when we start from V and move upwards, the first branching node we reach is V'1. This node dominates the NP the book and it does not dominate the PP in the store. By the same token the P in c-commands the NP the store; it does not c-command the V'1 buy the book, nor the V and the NP contained in V'1, because the first branching node dominating P does not dominate V'1.

(iii)

```        VP
|
V'2
|\
| PP
|   \
|    P'
|    |\
V'1  | \
|\   P  NP
| \  |   |
|  \ in the store
|   \
V   NP
|   |