Rooted Trees & Family Terminology (Parent, Child, Ancestor) | Discrete Mathematics §11.1

Parent, child, sibling, ancestor, descendant — the vocabulary of trees was borrowed wholesale from the genealogy charts people had been drawing for centuries. Pick one vertex to be the root and a plain tree turns into a family history. In this video: rooted trees and their terminology, built on the board. Choose a root, and because there is a unique path from it to every vertex, each edge gets a direction away from the root — that is a rooted tree. Pick a different root and you get a different rooted tree from the same underlying graph. We work through a thirteen-vertex example: reading off the parent of a vertex, the children of a vertex, siblings, the chain of ancestors up to the root, and the full set of descendants. We circle every leaf (no children) and mark the internal vertices, then box the subtree hanging below a chosen vertex. Hierarchy, drawn. This video is part of Discrete Mathematics · Trees (§11.1 — Introduction to Trees). Full section playlist linked above / in the description on the channel. Made with the Engineering Simplified method: a calm, two-voice story lesson taught on a chalk-and-board, with every definition and example drawn out step by step. Topic coverage follows Rosen, Discrete Mathematics and Its Applications (Chapter 11).