Mechanical device and Ratch

Mechanical device noun - Mechanism consisting of a device that works on mechanical principles.

Ratch and mechanical device are semantically related. In some cases you can replace term "Ratch" with "Mechanical device", this terms are similar.

Ratch noun - Mechanical device consisting of a toothed wheel or rack engaged with a pawl that permits it to move in only one direction.

Mechanical device and ratch are semantically related. You can use "Mechanical device" instead a noun "Ratch".