Elasticity of A Function - Semi-elasticity

Semi-elasticity

A semi-elasticity (or semielasticity) gives the percentage change in f(x) in terms of a change (not percentage-wise) of x. Algebraically, the semi-elasticity S of a function f at point x is

An example of semi-elasticity is modified duration in bond trading.

The term "semi-elasticity" is also sometimes used for the change if f(x) in terms of a percentage change in x which would be

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