(computing) The single node of a tree that has no parent.
(morphology) The primary lexical unit of a word, which carries the most significant aspects of semantic content and cannot be reduced into smaller constituents. Inflectional stems often derive from roots.
(philology) A word from which another word or words are derived.
(music) The fundamentaltone of any chord; the tone from whose harmonics, or overtones, a chord is composed.