Active Coils - Those coils which are free to deflect under load.

Allow for Set - Spring is supplied longer than specified to compensate for length loss when fully compressed in assembly by customer. Usually recommended for large quantity orders to reduce cost.

Baking - Heating of electroplated springs to relieve hydrogen embrittlement

Belleville Springs - These are essentially initially coned disk, who may be stacked up to give a variety of load-deflection characteristics.

Buckling - Bowing or lateral deflection of compression springs when compressed, related to the slenderness ratio.

Closed ends - Ends of springs where the pitch of the end coils is reduced so that the end coils touch.

Close-wound - Coiled with adjacent coils touching.

Compressive stress - Is the stress state when the material tends to compact (volume decrease). A simple case of compression is the uniaxial compression induced by the action of opposite, pushing forces. Most materials can carry compressive stress,

Deflection - Motion of the spring ends or arms under the application or removal of an external load.

Ductility - Being capable of sustaining large plastic deformations without fracture. It is characterized by the material flowing under shear stress.

Elastic deformation - Is the spring-like deformation, where a material will return to its original shape - see also Plastic deformation

Elastic limit - Maximum stress to which a material may be subjected without permanent set.

Elastic modulus - See Young's modulus

Endurance limit - Maximum stress at which any given material may operate indefinitely without failure for a given minimum stress.