Fundamental, a.
Etymology: [Cf. F. fondamental.]
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 axiom. The fundamental reasons of this war. Shak. Some fundamental antithesis in nature. Whewell. Fundamental bass (Mus.), the root note of a chord; a bass formed of the roots or fundamental tones of the chords. -- Fundamental chord (Mus.), a chord, the lowest tone of which is its root. -- Fundamental colors, red, green, and violet-blue. See Primary colors, under Color.
1 other Webster entry under this spelling
Fundamental, n.
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.
Shades of meaning
Fernald has no entry of its own for fundamental; he lists it under radical.
Where he writes about it:
The widely divergent senses in which the word radical is used, by which it can be at some time interchanged with any word in the above list, are all formed upon the one primary sense of having to do with or proceeding from the root (L. radix); a radical difference is one that springs from the root, and is thus constitutional, essential, fundamental, organic, original; a radical change is one that does not stop at the surface, but reaches down to the very root, and is entire, thorough, total; since the majority find superficial treatment of any matter the easiest and most comfortable, radical measures, which strike at the root of evil or need, are apt to be looked upon as extreme. — from radical