I learnt about this wave in school as a Sine Wave or a Sinusoidal Wave.
This is what Wikipedia has to say about it, "The sine wave or sinusoid is a mathematical function that describes a smooth repetitive oscillation. It occurs often in pure and applied mathematics, as well as physics, engineering, signal processing and many other fields."
Yup... it occurs in many other fields. Take HAPPINESS for example.
I've learnt that... happiness is a wave... and...
although happiness is always noted at its highest-point,
it is always IN RELATION to something at a lower-point.
If happiness is at its highest-point all the time, it will NOT
be happiness for long... because there will be NO Wave,
and NO WAVE will just be just another Boring Flat Line.