Domicile
A planet is in domicile when it occupies the sign it rules — its own house. It is the strongest of the five essential dignities, worth five points, and it describes a planet with full command of its own resources rather than a planet guaranteed a good outcome.
The fuller picture
The lookup is fixed and small. Seven planets rule the twelve signs: Mars has Aries and Scorpio, Venus has Taurus and Libra, Mercury has Gemini and Virgo, Jupiter has Sagittarius and Pisces, Saturn has Capricorn and Aquarius, and the two lights take one each — the Sun has Leo, the Moon has Cancer. A planet standing anywhere in a sign it owns is in its domicile, and that is the top of the dignity ladder at five points, above exaltation's four.
What it describes is autonomy. The images the tradition reaches for are all about ownership of the ground: a king in his own castle with the power to direct his affairs, able to move freely and safely, with nothing to fear; a queen inside her castle who can do what she wants and needs nobody's permission. Read on the person asking, that is someone with real agency in their own situation. Read on the thing asked about, it says the matter itself is in good order — a domiciled ruler of the ninth in a travel question means the trip is not the problem, whatever else in the chart is.
Three qualifications get dropped from short definitions, and each of them changes a reading. First, domicile is essential strength only, so it doesn't cancel an accidental affliction sitting on top of it: a planet retrograde in its own domicile reads as someone ill at home, taking a step forward and two back, and a domiciled ruler of the second can describe money that is genuinely there while a malefic in the same house blocks the person from reaching it. Second, the sign's own nature can void the dignity on the question's own subject — a domiciled significator in a barren sign, in a question about conceiving, describes someone healthy in every respect except the one being asked about. Third, domicile is the strongest kind of reception, and reception has a condition attached: two planets sitting in each other's domiciles with no aspect between them are not in mutual reception at all but in each other's generosity, which the tradition treats as weaker and separate.
One planet can hold domicile and exaltation at once — Mercury in Virgo is the standing example — and that pair is the strongest essential state available, scored nine. The other thing worth carrying away is structural: the planet ruling the sign a planet stands in is its dispositor, so domicile is the hinge the whole reception apparatus turns on. When you want to know who has a claim on a planet, the domicile owner of its degree is the first name to read.
In your chart
iHorary's dignities table gives domicile its own column, scored five, with a running total per planet, and the planet dossier names Domicile first when a planet holds it. The dossier also names that planet's dispositor — the domicile owner of the sign it occupies — reports whether an aspect actually connects the two, and says whether the dispositor is itself in its own dignity or in detriment or fall, because a lord in fall cannot lend what it hasn't got.
Ask a question and cast a chart