Day House/Triplicity - A House or Triplicity being diurnal rather than nocturnal and any diurnal Planet placed in it has more power in it than a nocturnal.

Debility/Debilitated - A Planet that is not in its Essential or Accidental dignities is considered Debilitated. This is especially true when a Planet is in its Fall or Detriment. Debilities or being debilitated makes Planets more malevolent then they naturally are inclined towards.

Decan/Decanate - A decan is a 10 degree division of each of the signs. There are 36 decans in the Zodiac. They are also called Faces of the Zodiac signs.

Decreasing in Light - When the Moon starts separating from an opposition from the Sun (also called a Full Moon) her light decreases gradually until she makes a conjunction with him (a New Moon). This phase of the Moon is also called Waning.

Degrees - Markers that divide each sign of the zodiac up into 30 parts, or the entire zodiac into 360 parts. Specific degrees have different meanings and interpretations.

Depositor - A Planet which is ruled under the sign that another Planet is placed in. For example, if Mercury is placed in Libra, Venus is the Depositor of Mercury.

Descendant - Another name for the 7th House. Also the point in which the Sun sets in the sky also being called the Western Angle. This angle is opposite to the Ascendant.

Detriment - The greatest Essential Debility to any Planet. It is found to be the opposite sign to the Planets House.

Dexter - The progression opposite to that of the direction of the signs. For example Gemini, Taurus, Aries.

Dignity/Dignities - A benevolent quality bestowed upon the Planets when they are happy in the positions they possess.

Dragons Head - The north node of the Moon and a benevolent point in a chart. The Dragons Head possess the benevolent nature of Jupiter.

Dragons Tail - The south node of the Moon and a malevolent point in a chart. It is 180 degrees opposite to the Dragons Head and possesses the malevolent nature of Saturn.