An undesirable optical effect found in halftone reproductions resulting from interference patterns caused by incorrect screen angles. Moiré patterns (in optics, called the moiré effect, and named after a type of woven fabric also called "moiré," etymologically deriving from the word "mohair") are characterized by the appearance of lines or dots at points where different sets of halftone lines or dots conflict, the points of conflict serving to reinforce the undesirable optical pattern. Also spelled "moire," without the accent over the "e," but always pronounced "mwah-RAY." See Screen Angles.
An undesirable moiré pattern is also found in television and video images, also caused when two patterns interfere. This is most often seen when a person in a televised image wears a finely-striped jacket or short. The odd vibrating effect seen between the stripes is an example of moiré.