What do you call the grouping of a parent and its child in a tree?

In the context of tree data structures, a subtree specifically refers to a portion of the tree that consists of a node and all of its descendants. When you look at a parent node and its child (and all further descendants under that child), this entire section of the structure can be viewed as a subtree. It retains the hierarchical relationships found in the larger tree while encapsulating a part of it.

The concept of a subtree is fundamental in various computer science applications, such as in searching algorithms, where the tree's structure can be effectively utilized to manage and navigate data hierarchies. Understanding this term helps in comprehending operations like traversal, insertion, and deletion within tree data structures, which often leverage the notion of subtrees to simplify processes.

Other terms like "Node," "Branch," and "Tree" describe different elements or characteristics within tree structures but do not encapsulate the relationship of a parent and its children in the same way that "Subtree" does. This precision in vocabulary enriches the understanding of tree data structures as a whole.