Molding is the American spelling of British moulding. You will meet it in two main places, and they are not equally obvious. In a house, a molding is a shaped strip — usually wood, plaster, or a light foam — that runs along a wall, a ceiling, a door, or a picture frame. It is there to look finished, not to hold the building up. In Taiwan, shops often still say 線板 even when the English on the pack says molding. In a factory, molding is the work of shaping something in a mold: plastic molding, injection molding. The piece that comes out can also be called a molding. So one spelling, two worlds: a pretty line in a room, and shaping in a factory. American English uses molding for both; British English uses moulding. It is not the fuzzy growth on bread — that is mold, or moldy bread.