Ratti
The traditional Indian unit for gemstone weight, taken in today's trade as about 0.91 carat, or roughly 180 milligrams.
Ratti takes its name from the gunja, the red and black seed historically used as a counterweight because the seeds are so consistent in mass.
The modern gem trade works to about 0.91 carat per ratti. Older systems, where 8 ratti made a masha and 12 masha a tola, imply a lighter ratti of around 0.12 grams.
Astrological prescriptions are almost always written in ratti rather than carat, which is why the unit survives in daily use.
When you are buying
Confirm which ratti a seller is using before agreeing a price, because the two conventions differ by roughly a third. The common astrological guideline is one ratti per twelve kilograms of body weight, but take the prescription from your astrologer rather than a chart on a shop wall.
Carat
A unit of gemstone weight, equal to 0.2 grams. Nothing to do with karat, which measures gold purity.
Tola
A traditional South Asian weight, about 11.66 grams. Still used in conversation, rarely on the bill.
Moti
The Hindi word for pearl, and in Vedic astrology the gemstone of the Moon, worn to strengthen Chandra.
Dosham-Free Pearl
A pearl free of the specific flaws that Vedic astrology considers inauspicious: cracks, pits, spots and irregular colour.
Moon Dasha
The planetary period ruled by the Moon in Vedic astrology, during which a pearl is most commonly prescribed.