A structure or finding in an experiment or investigation that is not a true feature of the object under observation, but is a result of external action, the test arrangement, or an experimental error.
(biology) A structure or appearance in protoplasm due to death, method of preparation of specimens, or the use of reagents, and not present during life.
An object made or shaped by some agent or intelligence, not necessarily of direct human origin.
(computing) A perceptibledistortion that appears in a digital image, audio or video file as a result of applying a lossy compression algorithm.