Declination
Declination is a body's distance north or south of the celestial equator, the second coordinate that zodiacal longitude alone leaves out.
Two planets at the same declination on the same side are in parallel, and on opposite sides in contraparallel. Tradition reads the parallel like a conjunction and the contraparallel like an opposition, and both can be exact between bodies that show no zodiacal aspect at all.
Because the Sun's declination is what makes the seasons, its extremes at the solstices, about 23 and a half degrees, bound the range that any body near the ecliptic can reach. A planet out of bounds beyond that is read as operating outside the usual rules.
Frequently asked
Can two planets be parallel without being in aspect?
Yes, and that is the point of looking. A parallel is measured in a different coordinate, so it can be exact where the zodiac shows nothing.
What does out of bounds mean?
A declination beyond the Sun's own maximum of about 23 and a half degrees, which classical and modern authors alike read as unusually free behaviour.