FUNDAMENTAL

I. adjective Date: 15th century 1. serving as an original or generating source ; primary , serving as a basis supporting existence or determining essential structure or function ; basic , 2. of or relating to essential structure, function, or facts ; radical , adhering to ~ism, of, relating to, or produced by the lowest component of a complex vibration, of central importance ; principal , belonging to one's innate or ingrained characteristics ; deep-rooted , see: essential ~ly adverb II. noun Date: 1637 something ~, 2. the principal musical tone produced by vibration (as of a string or column of air) on which a series of higher harmonics is based, the root of a chord, the harmonic component of a complex wave that has the lowest frequency and commonly the greatest amplitude