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Related to nodes: Lymph nodes
nodesThe two points at which the orbital plane of a celestial body intersects a reference plane, usually the plane of the ecliptic or celestial equator. When the body, such as the Moon or a planet, crosses the reference plane from south to north it passes through the ascending node; crossing from north to south the body passes through its descending node. The line joining these two nodes is the line of nodes.
A celestial body might not cross the reference plane at the same points every time: the line of nodes then moves slowly forward or backward around the orbital plane, i.e. in the same or in the opposite direction to the body. This is termed progression or regression of the nodes. The Moon's nodes regress along its orbital plane, making one complete revolution in 18.61 years. This period is equal to the period of nutation.