Binary Trees Terminology

leaves: nodes with no children.
siblings: nodes with the same parent.
depth of node: number of edges from the root to the node
height of node: number of edges from the node to the deepest leaf
height of tree: height of the root
full binary tree: a binary tree in which each node has exactly zero or two children
complete binary tree: a binary tree which is completely filled, with the possible exception of the bottom level, which is filled from left to right.

Leaf

A node with no children

The depth of a node is the number of edges from the node to the tree’s root node. A root node will have a depth of 0.

The height of a node is the number of edges on the longest path from the node to a leaf. A leaf node will have a height of 0.

The height of a tree would be the height of its root node, or equivalently, the depth of its deepest node.

The diameter (or width) of a tree is the number of nodes on the longest path between any two leaf nodes.