Elements
Each sign of the zodiac is associated with one of the 4 elements: Fire, Earth, Air or Water. These signs share common characteristics.
Qualities
In a similar way, each of the zodiac signs is also associated with one of the 3 qualities.
Dualities
The astrological Duality is not to be confused with the literal (and more sexist) view of masculine/feminine. It expresses how energy is experienced and directed in relationship with the environment.