Moiré Pattern
Definition
The strange wavy bands that appear when two fine grids overlap — like filming a striped shirt or stacking window screens.
Technical definition
Beating between two periodic structures of slightly different pitch or angle produces a low-frequency envelope pattern.
Example
TV presenters avoid pinstripe suits — the camera's pixel grid beating against the fabric stripes creates crawling moiré on screen.
Common confusion
Moiré is not a defect in either pattern — both grids are perfect. The bands emerge purely from superposition, like acoustic beats.