Sect
Sect is the division of a chart into day or night, decided by whether the Sun is above or below the horizon, and it changes which planets are favoured.
In a day chart the Sun, Jupiter and Saturn belong to the sect in favour; in a night chart it is the Moon, Venus and Mars. Mercury takes the side of whichever it rises with. A planet in its own sect works in better conditions than the same planet out of sect.
Sect is the first thing a traditional reading establishes, because it decides the triplicity rulers and colours how the benefics and malefics behave for the whole chart.
Frequently asked
What if I was born at sunrise?
Then the Sun sits on the horizon and the chart is borderline; the exact birth time and the Ascendant degree decide it.
Does sect matter more than aspects?
It works differently: sect sets the conditions the whole chart operates under, while aspects describe specific relationships within it.