**Second-order** generally indicates an extended or higher complexity.
Specific uses of the term include:
in mathematics and logic

**Second-order** approximation, an approximation that includes quadratic
terms
**Second-order** arithmetic, an axiomatization allowing quantification of
sets of numbers
**Second-order** differential equation, a differential equation in which
the highest derivative is the second
**Second-order** logic, an extension of predicate logic
In perturbation theory, a second-order perturbation may be obtained
iteratively

in science and engineering

**Second-order** fluid, an extension of fluid dynamics
A second-order
**Fresnel lens**

Fresnel lens has a focal length of approximately
50 cm (19.7 in)
**Second-order** reaction, in chemical kinetics, a reaction in which the
rate is proportional to the square of a reactant's concentration

in psychology and philosophy

**Second-order** conditioning, a form of learning from previous learning
**Second-order** desire, the desire to have a desire for something
**Second-order** simulacra, a symbol with no real object to represent
**Second-order** stimulus, a visual stimulus distinguished by an aspect
other than luminance

in religion

Second Order (religious), the cloistered nuns who are affiliated with
mendicant orders of friars

This disambiguation page lists articles associated with the title
Second-order.
If an internal link led you here, you may wish to change the link to
point directly to the