The secular variations of the planetary orbits is a concept describing long-term changes (secular variation) in the orbits of the planets Mercury to Neptune. If one ignores the gravitational attraction between the planets and only models the attraction between the Sun and the planets, then with some further idealisations, the resulting orbits would be Keplerian ellipses. In this idealised model the shape and orientation of these ellipses would be constant in time. In reality, while the planets are at all times roughly in Keplerian orbits, the shape and orientation of these ellipses does change slowly over time. Over the centuries increasingly complex models have been made of the deviations from simple Keplerian orbits. In addition to the models, efficient and accurate numerical approximation methods have also been developed.