.
Here, i is in j's left subtree, and k is j's right subtree.
An n-node binary tree.
Not necessarily complete.
All nodes j (other than leaves) satisfy the ``binary-search-tree
property'': .
Here, i is in j's left subtree, and k is j's right subtree.
In terms of the array representation: 
.
Example...
Note: not enough that the property just holds for immediate children. Must hold for the entire family line.
