An Etymological Dictionary of Astronomy and Astrophysics

1. Math.: For a → function y = f(x), a point at which the → tangent to the graph is horizontal. In other words, a point where the → slope is zero: dy/dx = 0.
   

2. Of a planet, the position at which the rate of change of its apparent → right ascension is momentarily zero.

See also: → stationary; → point.