Of or relating to the foundation or base; elementary, Of or relating to the lowest possible frequency or the lowest frequency component of a vibrating element, system, periodic wave, or quantity, serving as an essential component, noun_ the lowest tone of a harmonic series, A leading or primary principle, rule, law, or article, which serves as the groundwork of a system; essential part, as, the fundamentals of linear algebra, The lowest frequency of a periodically varying quantity or of a vibrating system