A basic principle, rule, or law that serves as the groundwork of a system; an essential part. Understanding the fundamentals of mathematics is crucial for advanced studies in the subject.
A basic or essential quality or element. The fundamentals of good health include a balanced diet and regular exercise.
In acoustics and music, the principal or lowest tone of a harmonic series; the root note of a chord. The fundamental of the note was barely audible over the higher harmonics.