说明：  快速傅立葉變換，是快速計算序列的離散傅立葉變換或其逆變換的方法[1]。傅立葉分析將訊號從原始域（通常是時間或空間）轉換到頻域的表示或者逆過來轉換。FFT會通過把DFT矩陣分解為稀疏（大多為零）因子之積來快速計算此類變換。[2] 因此，它能夠將計算DFT的複雜度從只用DFT定義計算需要的O(n^{2})，降低到，其中n 為資料大小。
(The fast Fourier transform is a method for quickly calculating the discrete Fourier transform of a sequence or its inverse transform [1]. Fourier analysis converts the signal from the original domain (usually time or space) to the representation of the frequency domain or vice versa. The FFT quickly calculates such a transformation by decomposing the DFT matrix into a product of sparse (mostly zero) factors. [2] Therefore, it is able to reduce the computational DFT complexity from O(n^{2}), which is only required for DFT definition calculations, where n is the data size.)