Kolmnulgiku
Kolmnulgiku is a term found in some Estonian-language geometry and puzzle literature to refer to a three-angled polygon, commonly understood as a triangle. Etymology-wise, it comes from kolm (three) + nurg (angle) + -iku (a diminutive or shape-forming suffix). In formal mathematics, however, the standard term for this shape is kolmnurk, and kolmnulgiku is largely encountered in informal or educational contexts.
A kolmnulgiku is defined by three straight sides and three interior angles; in Euclidean geometry, the sum
History and usage of the term indicate that kolmnulgiku appears mainly in school materials, introductory texts,
Variants and related concepts: educational texts may present phrases such as väike kolmnulgiku (small triangle) or