Definition of aliasing

Answer 1

Aliasing is the effect of under-sampling a continuous signal, which causes frequencies to show up as different frequencies. This aliased signal is the signal at a different frequency. This is usually seen as higher frequencies being aliased to lower frequencies. For a 1d signal in time, the aliased frequency components sound lower in pitch. In 2d space, such as images, this can be observed as parallel lines in pinstripe shirts aliasing into large wavy lines. For 2d signals that vary in time, an example of aliasing would be viewing propellers on a plane that seem to be turning slow when they are actually moving at very high speeds