Plank is a long, flat piece of wood, usually sawn from a tree trunk and used for building. When pioneers built their cabins, they used thick planks for floors and walls. When pirates supposedly made prisoners walk the plank in old stories, they forced them onto a wooden board extending over the ocean.

Planks are thicker and sturdier than boards, which makes them perfect for construction projects where strength matters. A tree trunk gets sawed lengthwise into planks at a lumber mill, where enormous blades slice through the wood. Carpenters use planks to build decks, frame houses, and create furniture.

The word also describes a key principle or policy, especially in politics. When a political party writes its platform (its official positions), each major idea is called a plank in that platform. If someone runs for student council promising longer recess, that's a plank in their platform.

In fitness, a plank is an exercise where you hold your body rigid and straight like a wooden plank, balanced on your forearms and toes. It looks simple but requires serious core strength. When someone planks, they're either doing this exercise or lying flat and stiff (sometimes as a prank or internet trend, though that trend faded years ago).