Parallel of declination - This occurs when two planets are the same number of degrees of arc North or South of the Celestial Equator.
The Parallel of Declination is a different kind of Aspect, because it does not refer to the Planets' longitudinal positions but rather to their positions in Declination (North or South of the Celestial Equator).
At either pole a planet on any parallel of declination moves along an arc parallel to the equator, to the horizon of the pole.
A planet is inconjunct when it forms no aspect and is not in parallel of declination or mutual disposition to another planet.
The traditional astrological aspects - the conjunction, sextile, square, trine, and opposition - and parallel of declination, are important keys in determining weather patterns.
The concept behind the use of Antiscion Points is that a planet crossing one side of a pair of antiscia will be on a point that would be in parallel of declination were it the Sun.
The conversion degrees and planetary zodiacal longitude will only be the same when the planet is on the ecliptic. By the same token, any two planets at these two degrees will be in parallel of declination.
See also: Aspects, Venus, Mars, Conjunction, House