Inorder

Part of speech: adverb, adjective

Definitions

1. Describing a method of visiting every node of a binary tree by processing the left subtree, then the node itself, then the right subtree
2. Relating to a traversal of a binary tree that handles the left branch first, the current node next, and the right branch last
3. Characterizing the sequence in which a binary tree is walked, moving through the left child, the parent node, and then the right child

Etymology: The word "inorder" is a plain compound: the English preposition "in" joined to "order," which has come down through Old French "ordne" and Latin "ordinem," meaning a row, rank, or arrangement. Its meaning in the phrase "in order" is the sense of things arranged in sequence, and the tree-traversal sense grows naturally from that idea of a fixed sequence. The programming sense is what gives the word its specialised use. In a binary tree, the traversal visits the left subtree, then the node itself, then the right subtree, so the nodes are visited in their sorted sequence. The term describes that fixed sequence of visits rather than a new ingredient of meaning.