Definition: The wy (also known as the wye) is a 150m-long, straight, winding railway line in the United Kingdom. It runs from London to Liverpool and is one of the most famous and historic railway lines in the world. The wy was built by the London & North Western Railway (LNER) in 1846 as part of the Great Northern Line. Initially, it was a single track line but later became a double track line after the completion of the