Fundamental

a. [Fr. fondamental, Sp. fundamental, It. fondamentale. See supra.] Pertaining to the foundation or basis; serving for the foundation; hence, essential, as an element, principle, or law; important; original; elementary; as, a fundamental truth; a fundamental sound or chord in music. “The fundamental reason of that war.” Shak. “Some fundamental antithesis in nature.” Whewell.

Fundamental base (Mus.), a base formed of the roots or fundamental tones of the chords. — Fundamental chord (Mus.), a chord, the lowest tone of which is its root.