The term "keel" refers to the structural component of a ship or boat that runs along the bottom from the bow to the stern. It provides stability and strength, helping to keep the vessel upright in the water. The keel is often considered the backbone of the ship, as it supports the hull and helps to prevent capsizing. In addition to its role in maritime design, "keel" can also refer to a similar structure in aircraft, known as the vertical stabilizer. This part helps maintain directional stability during flight, much like the keel does for a ship. Both structures are essential for the safety and performance of their respective vehicles.