n.
Function: noun
Date: 1637
1 : something fundamental especially : one of the minimum constituents without which a thing or a system would not be what it is
2 a : the principal musical tone produced by vibration (as of a string or column of air) on which a series of higher harmonics is based b : the root of a chord
3 : the harmonic component of a complex wave that has the lowest frequency and commonly the greatest amplitude