Sisäsolmua

Sisäsolmua is a Finnish term used in mathematics, computer science and related fields to denote an internal node in a tree or network structure. In rooted trees, sisäsolmu refers to a node that has at least one child, i.e., a non-terminal node. In unrooted trees, the concept is often described as a node with degree greater than one, meaning it is not a leaf.

The concept plays a central role in various data structures and algorithms. In binary search trees, tries and parse trees, sisäsolmua are the nodes that guide traversal and decision making. They represent branching points or decision tests, while leaves (the terminal nodes) represent endpoints or final results. In phylogenetic trees and other hierarchical models, internal nodes (sisäsolmu) typically correspond to ancestral states or branching events.

In Finnish usage, the term is commonly contrasted with solmu that denotes a node without descendants or a terminal point. The word sisäsolmua is grammatically the partitive singular form of sisäsolmu, and appears in scientific writing to specify “an internal node” within a larger structure. The concept is language-agnostic in its mathematical meaning, but the Finnish term is used to express the same idea concisely in technical discussions.

See also: solmu (node), puu (tree), solmujako in graph theory (various node classifications).