Fundamental /(?)/

Fun·da·men·tal

Fundamental

a.
  1. Pertaining to the foundation or basis; serving for the foundation.
    The fundamental reasons of this war.
    Some fundamental antithesis in nature.

Phrases & Compounds
Fundamental bass
the root note of a chord; a bass formed of the roots or fundamental tones of the chords.
Fundamental chord
a chord, the lowest tone of which is its root.
Fundamental colors
red, green, and violet-blue. See Primary colors, under Color.

Fundamental

n.
  1. A leading or primary principle, rule, law, or article, which serves as the groundwork of a system; essential part, as, the fundamentals of the Christian faith.