Keep in mind that, in general, you need an infinite number of Fourier bases to represent an arbitrary waveform. But if you want to use a finite number of bases

Keep in mind that, in general, you need an infinite number of Fourier bases to represent an arbitrary waveform. But if you want to use a finite number of bases (and indeed as small of a number as you can get away with), and if the waveform you wish to represent has known structure, there can be more efficient representations.