Question for /sci/ about waves. So as most of you probably know, you can represent most periodic signals by their trigonometric (or exponential) Fourier series. Using the Fourier series, you can easily analyze the signals using Fourier analysis, which shows all the different harmonics and so on. But you're not limited to representing a periodic signal using sinusoidal functions. You could theoretically also represent any periodic functions as a sum of square waves. Looking at any wave form in terms of sinusoid is really useful, especially for signal processing. But the signal can be represented in other basis. So its wrong to say that a specific signal is "made up" of different sinusoidal harmonics, since it can be represented in terms of square harmonics. Is there a "fundamental" basis which every other waves are derived from, or can you simply pick any basis you want as long as it's convenient. What I'm trying to ask is whether there is a waveform such that all other periodic signals are derived from it and it's harmonics.