The three Qualities defined in Astrology are, after the Elements, the second major classification that defines the nature of the Signs. The Qualities assign the Signs into Quadruplicities, groups of four Signs each that reflect the three common modes of Signs.
Within an astrological chart, the Quality describes a person's attitudes in life and the way they approach projects. The three Qualities are Cardinal, Fixed and Mutable.
The Cardinal Signs are Aries, Cancer, Libra and Capricorn. These four Signs are the initiators of the Zodiac. Their common characteristics include action and drive; they have initiative and strong motivation. On a team, Cardinal Signs are the people who come up with ideas and get the project moving, but they are not very good at completion and follow-through. The Cardinal Houses are the First, Fourth, Seventh and Tenth; if a chart has a number of Planets in these Houses, the chart is weighted toward Cardinal energy.
The Fixed Signs are Taurus, Leo, Scorpio and Aquarius. These four Signs are the members of the Zodiac who dedicate themselves to seeing projects through to completion. Their common characteristics include determination and persistence; they are stable and self-reliant. On a team, Fixed Signs are the people who keep a project going and see it through to the end, but they can also be stubborn and inflexible. The Fixed Houses are Second, Fifth, Eighth and Eleventh; if a chart has a number of Planets in these Houses, the chart is weighted toward Fixed energy.
The Mutable Signs are Gemini, Virgo, Sagittarius and Pisces. These four Signs are the flexible members of the Zodiac, happy to fill an assigned role. Their common characteristics include adaptability and changeability; they are flexible and versatile. On a team, Mutable Signs adapt easily to changing conditions, and they don't have a particular agenda. They can, however, be wishy-washy or inconsistent. The Mutable Houses are Third, Sixth, Ninth and Twelfth; if a chart has a number of Planets in these Houses, the chart is weighted toward Mutable energy.
Many people don't realize how important the Elements and Qualities are in true Astrology. It's the combination of Elements and Qualities that makes the Signs what they are; they combine in twelve distinct ways, one for each Sign.