### secular

(occurring slowly over a long period of time)

**Secular**, as used in astronomy, indicates occurrence
over a long period of time and not periodic.
It is especially used to discuss the long-term trends
in a motion that is periodic over the shorter term,
such as stating that/how an orbit changes over time.

The term is commonly used in describing dynamics and orbits.
Some phrases:

- "secular variation"
- "secular phenomena"
- "secular perturbation"
- "secular chaos"
- "secular acceleration"
- "secular drift"

The term is also used in time series analysis, with an analogous meaning.

(*astronomy,dynamics,orbits,kinematics*)
http://en.wikipedia.org/wiki/Secular_phenomena

**Referenced by:**

gravitational instability (GI)

Jacobi integral

Laplace-Lagrange secular theory

orbital resonance

parallax

perturbation theory

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