Rashi
every reader
What the tradition reads
A rashi is a sign of the sidereal zodiac, one of twelve equal thirty degree divisions of the ecliptic measured, unlike the Western tropical sign, against the actual visible constellations rather than against the equinox, so that a rashi and its similarly named tropical counterpart can point to noticeably different stretches of sky once the ayanamsa between them has grown large enough. The tradition builds the whole sign house system directly from the rashi the ascendant occupies: the Swiss Ephemeris describes that method as a first house beginning at the start of the sign the ascendant is in, each house covering a complete sign, used in Hellenistic astrology and still used in Hindu astrology, so the twelve houses run one to a rashi rather than following any finer division of the zodiac. Each rashi carries the same basic attributes as its tropical counterpart, a ruling planet, an element and a modality, but because sidereal placements can differ from tropical ones, especially for planets sitting close to a sign boundary, the two zodiacs can occasionally place the same birth moment's Sun, Moon or ascendant in different rashis and signs entirely.
The story
Rashi is the ordinary Sanskrit word for a part, a heap, or a portion, used elsewhere in the language for any quantity divided into shares and narrowed in astrology to name specifically one of the twelve equal parts into which the ecliptic circle is cut. Whether the twelve rashi scheme itself, and the horoscopic technique built on top of it, entered Indian astrology through contact with Hellenistic astronomy in the early centuries of the common era is, in Wikipedia's own words, a point of intense debate: some scholars hold that Indian horoscopic astrology came from Hellenistic influence, while others argue Jyotisha developed independently, even if it may have interacted with Greek astrology. What is not disputed is that the twelve sign zodiac, however it arrived, sits alongside an older, more indigenous twenty seven nakshatra scheme the Vedic tradition had already used for centuries to track the Moon's own nightly progress, and the two schemes have coexisted ever since without either displacing the other, so that a single sidereal degree in a modern Vedic chart carries both a rashi and a nakshatra drawn from that older lunar calendar.
Written from
Corpus key glossary:rashi.