The public face of New York’s diamond district is Diamond and Jewelry Way, a block of 47th Street between Fifth and Sixth Avenues lined with dazzlingly lit shops and exchanges and cluttered by hawkers, hustlers, cops and couriers. But beyond these street-level operations, in back rooms, upper floors and looming towers, toils an army of cutters, blockers, polishers, sorters, appraisers, graders, designers and dealers — most of whom the diamond-buying public never sees.

Or hears. The street has its own vocabulary, honed over generations and still used today. The prevalence of Yiddish reflects the historic influence of Jewish craftsmen and dealers. But the diamond business is international, and on Diamond and Jewelry Way it is not uncommon to hear Russian, Indian, Dutch, French, Belgian, Korean and other accents enunciating the mame-loshn (literally, “mother tongue”) of Eastern European Jewry, and a few non-Yiddish phrases as well.

Diamond sellers, or diamantaires, deploy an extensive nomenclature of technical terms to describe their wares — not just the famous Four C’s of color, clarity, cut and carat weight, but also dimensions, fluorescence, inclusions (flaws), polish and symmetry. Traders will instantly know what the description “round G 4.18 VVS₂ TRIP X” means, as well as the diamond’s value. On examination, they can judge if that stone’s color is a “good G” or “low G” and whether its clarity is actually the inferior VS₁. These terms may be tricky to decipher (and trickier still to apply commercially), but they are widely known. In the business, however, there are many other words to describe what really matters about a given stone, or shteyn (Yiddish), steen (Dutch), pierre (French), almaz (Russian) or hira (Hindi).

Unless otherwise noted, all non-English terms are Yiddish or are derived from Yiddish and are rendered using the transliteration system developed by the YIVO Institute for Jewish Research.