Mithuna

Mithuna is the third rashi, the Vedic sign of the twins or the couple, corresponding to Gemini. In jyotisha it is ruled by Mercury (Budha). Its quality is dual or mutable (dvisvabhava), and its element is air (vayu tattva). Jyotisha reads Mithuna through Mercury's versatility: communication, curiosity, exchange, and the two-sided, adaptable nature the twins symbolise. As a sidereal sign it is fixed to the stars and sits roughly 24 degrees behind the tropical Gemini. Mercury's rulership of the twins is common to Western and Vedic astrology alike. Jyotisha then reads a planet placed here through the additional machinery the tradition supplies, the nakshatra it falls in, the divisional charts, and the planetary period (dasha) then running, so the sign is only the first layer of a much denser interpretive system.

Mithuna translates as a pair or a couple rather than specifically twins, a subtly different sense from the Greek didymoi it renders, which does mean twins outright, and the Sanskrit name reflects the general fact of pairing more than the specific mythological brothers Castor and Pollux the Greek sign evokes. That transmission runs through the Yavanajataka, a Sanskrit versification of a Greek astrological text of roughly the second through fourth centuries CE, though the twelve equal signs themselves originate earlier still, in Babylonian celestial divination of roughly the fifth or fourth century BCE, with no twelve-sign zodiac of any kind attested in the older Vedic corpus. Mercury's rulership of Mithuna, shared with the tropical Gemini, belongs to a later classical layer, standardly credited to compilations such as the Brihat Parashara Hora Shastra of the seventh or eighth century CE.

Sources Brihat Parashara Hora ShastraSage Parashara (attributed) with The Yavanajataka of SphujidhvajaDavid Pingree, Jyotihsastra: Astral and Mathematical LiteratureDavid Pingree

Budha, Mercury, owns Mithuna. As with every rashi, the house that Mithuna occupies is read through the condition of its lord wherever that lord is placed, so Mithuna in a chart is always a redirection to Budha rather than a self-contained statement.

Mithuna is one of the signs to which no planet is assigned either exaltation or debilitation. Seven grahas have an exaltation sign and a debilitation sign, which accounts for fourteen of the twenty four available slots across twelve signs, and the remainder are left empty. Mithuna, Simha, Dhanu and Kumbha carry none. This is worth stating plainly because absence is easy to misread as an oversight: a planet in Mithuna is assessed by lordship, by aspect, by the divisional charts and by its nakshatra, but not by any dignity belonging to the sign itself.

Three nakshatras cross it. Mrigashira supplies its last two quarters, Ardra lies wholly within, and Punarvasu contributes its first three quarters before passing into Karka. Ardra is ruled by Rahu in the vimshottari scheme and Punarvasu by Guru, so a planet moving through Mithuna passes from a Mars-ruled mansion through a Rahu-ruled one into a Jupiter-ruled one within a single sign. That sequence matters in practice because the nakshatra lord determines which dasha period a birth falls into, and two people born days apart under the same rashi can begin their lives in entirely different planetary periods.