secular

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 or secular motion
• "secular phenomena"
• "secular perturbation"
• "secular chaos"
• "secular acceleration"
• "secular drift"

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