Definitions of terminology

ATEX; The ATEX directives are two EU directives describing the minimum safety requirements for workplaces and equipment used in atmospheres. The name is an initialisation of the French term Appareils destinés à être utilisés en ATmosphères EXplosives (French for "Equipment intended for use in explosive atmospheres").
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Examples: bellhousings, disc couplings, JXL couplings, all steel gear couplings,

Backlash free or anti-backlash is the prevention of the occurrence which is achieved in different ways depending on the type of component.

Examples: bellows couplings, spider couplings, servomate couplings, servoplus couplings

Fottinger Principle; The Föttinger principle ( Föttinger converter , Föttinger gearbox , torque converter ) in its original form consists in the coupling of a drive shaft with an output shaft via a circulating fluid (oil, water, etc.) to transmit a rotary movement (a ). For this purpose, a pump wheel (connected to the drive shaft) and a turbine wheel (connected to the output shaft) are arranged rotatably (mostly in alignment) in a sealed, fluid-filled housing at a short distance, but without contact, with the fluid flow from the outlet of the turbine wheel via a stationary Guide device is returned to the input of the pump wheel. The wheels and the guide device are designed in such a way that the fluid flow takes place on curved paths with a continuous change in curvature, so that a largely shock-free and loss-free flow can be achieved.
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(Source: https://second.wiki/wiki/fc3b6ttinger-prinzip)

Examples: Fludex® coupling

FRAS; abbreviation for fire resistant and anti-static

Examples: tyre couplings

NEMA; abbreviation for the National Electrical Manufacturers Association. An example of NEMA is a rating that is used as a standard to define the types of environments where an electrical device can be used; a NEMA rating. abbreviation.

Examples: bellhousings

Prime Mover; an initial source of motive power (such as a windmill, waterwheel, turbine, or internal combustion engine) designed to receive and modify force and motion as supplied by some natural source and apply them to drive machinery.

Restorative Force; eg: Compensation for shaft misalignment with low restorative forces.
In physics, the restoring force is a force which acts to bring a body to its equilibrium position. The restoring force is a function only of position of the mass or particle, and it is always directed back toward the equilibrium position of the system. The restoring force is often referred to in simple harmonic motion. The force which is responsible to restore original size and shape is called restoring force.
An example is the action of a spring.  An idealized spring exerts a force that is proportional to the amount of deformation of the spring from its equilibrium length, exerted in a direction to oppose the deformation. Pulling the spring to a greater length causes it to exert a force that brings the spring back toward its equilibrium length. The amount of force can be determined by multiplying the springs’ constant factor characteristic of the spring by the amount of stretch, also known as the Hooke's Law.Another example is of a pendulum. When the pendulum is not swinging all the forces acting on the pendulum are in equilibrium. The force due to gravity and the mass of the object at the end of the pendulum is equal to the tension in the string holding that object up. When a pendulum is put in motion the place of equilibrium is at the bottom of the swing, the place where the pendulum rests. When the pendulum is at the top of its swing the force bringing the pendulum back down to this midpoint is gravity. As a result, gravity can be seen as the restoring force in this.
Source: https://en.wikipedia.org/wiki/Restoring_force

PTO; A power take-off or power takeoff (PTO) is any of several methods for taking power from a power source, such as a running engine, and it to an application such as an attached implement or separate machine.

Examples: splitter gearboxes, ‍

Service Factor; The service factor, SF, is a measure of periodical overload capacity at which a coupling can operate without damage. A coupling operating continuously at a service factor greater than 1 will have a reduced life expectancy compared to operating at its rated power.

Examples: service factor table, ‍

Side Loads; A power take-off or power takeoff (PTO) is any of several methods for taking power from a power source, such as a running engine, and it to an application such as an attached implement or separate machine.

Examples: splitter gearboxes, ‍

Torsionally Rigid; The applied torque needed to produce a unit angle of twist in a circular elastic material; a measure of a body's resistance to torsion.

Torsional rigidity is a measurement of torque per angular displacement, and may be expressed as follows:
Ct = Torsional Stiffness (Nm/rad) Ct = M/ѱ Where: M = Torque (Nm) and ѱ = Angular Displacement (rad).

Examples: rigid shaft couplings, bellows couplings, disc couplings, all steel gear couplings

VDMA; Verband Deutscher Maschinen- und Anlagenbau The VDMA is the association of Germany's engineering industry. It represents the interests of Germany's large capital goods sector, including machinery, plants, system suppliers, system integrators and service providers. Acronym: VDMA. Website: www.vdma.org

Examples: bellhousings