In this paper, we characterize the noise in Kinect depth images based on multiple factors and introduce a uniform nomenclature for the types of noise. In the process, we briefly survey the noise models of Kinect and relate these to the factors of characterization. We also deal with the noise in multi-Kinect set-ups and summarize the techniques for the minimization of interference noise. Studies on noise in Kinect depth images are distributed over several publications and there is no comprehensive treatise on it. This paper, to the best of our knowledge, is the maiden attempt to characterize the noise behavior of Kinect depth images in a structured manner. The characterization would help to selectively eliminate noise from depth images either by filtering or by adopting appropriate methodologies for image capture. In addition to the characterization based on the results reported by others, we also conduct independent experiments in a number of cases to fill up the gaps in characterization and to validate the reported results.