History: What is a sine wave?

What is a sine wave?

• A non-sinusoidal waveform named for its triangular shape.
  This describes a triangle wave.
• An integer multiple of the fundamental frequency.
  This is a harmonic.
• Not an integer multiple of the fundamental frequency.
  This is inharmonic.
• The simplest sound in the universe, defined as a periodic oscillation that follows a trigonometric function.
  Correct!