What is the ship's rear?

The rear of a ship is called the stern aft To go to the rear is called going aft. The aft most part is the stern The rear of a ship or boat is called the "Aft" or the "aft end". Examples: "Take that line aft!". "When we turn, are you sure the aft end will clear that bouy?" Also nautically, "avast"
The stern is the aft part of a ship or boat.