Wavelength of a sinusoidal wave is defined as the spatial period of the wave, which can be measured between any two points on the wave where the shape repeats. But if my wave is defined as a function of time (like those of a simple harmonic oscillator), how can you say the distance along the time axis is the wavelength? Am I measuring something else that just happens to be equal to the distance between two points in the same phase along the time axis? How can the time axis determine the wavelength of a wave? Also; isn't that distance the period? The amount of time it takes for the wave to complete one cycle? In which case the velocity of the wave would always equal one?