The rear suspension of a vehicle refers to the system of components that support and control the movement of the rear wheels. A semi-trailing arm geometry is a type of rear suspension design in which each wheel is mounted on a trailing arm that is connected to the vehicle's chassis by a pivot point. This system includes a control arm and a lateral link to maintain the position and alignment of the wheels while allowing them to move independently of each other.

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The semi-trailing arm geometry provides a good balance between ride comfort and handling performance. It allows for a greater degree of wheel movement than other suspension designs, which helps to absorb bumps and provide a smoother ride. At the same time, the system maintains good stability and control, which helps to enhance the vehicle's handling and driving characteristics. This design is popular due to its versatility, durability, and performance capabilities, and has been used in a wide range of vehicles, from small passenger cars to larger commercial vehicles and trucks.