Difference between frequency components and harmonic components - Fourier What is the difference between frequency components and harmonic components? The first concern the continuous domain of frequency, while the second concern the discrete domain of frequency ($f_{k}=kf_{0}$ with $f_{0}$ foundamental frequency)?

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Frequency components are $f_k$ for $k=1,\ldots,K$.  There is no relationship between them.

Harmonic components are $f_p$ for $p=1,\ldots,P$ and 
$$
f_p = p f_1
$$