MDF is a heavy, smooth board used to make cheap furniture, shelves, and cupboard doors. It is not a plank cut from a tree. Factories break wood into tiny fibres, mix them with glue, then press the mix with heat until it becomes a flat board. You can paint it, or stick a thin pretty layer on top, so a wardrobe may look like wood when it is MDF underneath. It is cheaper and more even than real wood, and it has no knots. The other side of the story is less kind: it is heavy, it hates water — if it gets wet it swells and crumbles — and screws do not hold in it as well as they do in solid wood. In shops and with builders, people just say MDF; it is a workshop word, not a fancy one. Though actually, “wood furniture” in a cheap shop is very often this, even when the picture on the box looks like a forest.