Encyclopedia of Vedic Astrology: Yogas

In Vedic astrology, the associations the planets form or variations of how they are placed in a horoscope are referred to as yogas. Yoga literally means union or that which adds, joins or yokes. Astrologically, Yoga refers to planetary combinations or configurations and their special results, which affect the life of an individual. In traditional Indian ephemeris, known as Panchang, Yoga is also a particular division of time, arrived at by adding longitudes of the Sun and the Moon at birth.
These are 27 in number, starting from Viskumbha to Vaidhriti, each governed by a different constellation or lunar-mansion, which are also 27 in number. In spiritual field, the word "Yoga" means training, taming and stimulating the body and mind with universal soul. In Ayurveda, the yoga of two or more medicines gives specific results. Yogas are one of the unique features of Vedic astrology. There are hundreds of yogas mentioned in various classical texts.
Most of the yogas are formed of more than one planet, but all combinations do not mean a yoga formation. The idea behind these yogas is to equate the planets' strength in a chart, and how when they will produce their effects in a native's life.