I was reading this question. Where the author made a statement that
If I take a wave with period T, it is also true that it has a period 2T, 3T and so on. That is, it has frequencies of 2π/T, but also 2π/2T and so on.
I know if I take a (quasi) monochromatic wave of frequency $\omega$ it do not contain the sub-harmonics ($\omega/2,\omega/3...$).
I also believe that the statement (as I have quoted above) given by the author should not be correct but can not figure out why it should be wrong.
My question is: what physical property of the wave prohibit the multiples of time period to be taken as the time period of wave, and if this statement is not true what prevent the presence of sub-harmonics in that wave.