In
signal processing, a
window function (also known as an
apodization function or
tapering function) is a
mathematical function that is zero-valued outside of some chosen
interval. For instance, a function that is constant inside the interval and zero elsewhere is called a
rectangular window, which describes the shape of its graphical representation. When another function or waveform/data-sequence is multiplied by a window function, the product is also zero-valued outside the interval: all that is left is the part where they overlap, the "view through the window".