What does culet mean?
A culet is a technical term with two distinct applications. In gemmology — its dominant modern use — it denotes the tiny flat facet polished across the bottom tip of a faceted gemstone such as a diamond, running parallel to the table on top. Historically, cutters left a noticeable culet to protect the stone's vulnerable point from damage, but contemporary cutting practice favours reducing it to a near-point, so graders describe culets as none, small, medium, or large, and a large one can appear as a dark circle through the crown. The word's older sense lies in armour history, where a culet was one of several overlapping steel plates guarding the lower back and rump beneath a breastplate's rear counterpart. Derived ultimately from Latin via French roots meaning 'rump' or 'bottom', the term remains firmly specialist: you will meet it in diamond certificates and museum armour catalogues far more often than in ordinary conversation.
nounIn gemmology, a culet is the small flat facet polished on the bottom (pavilion) of a cut gemstone, parallel to the table. In historical armour, a culet is a series of overlapping steel plates protecting the lower back and rump of a wearer.
- Gemmology: the small horizontal facet ground or polished at the very bottom point (pavilion) of a faceted gemstone, originally added to protect the fragile point from chipping; in modern cutting standards it is usually reduced to a point or kept extremely small.
- Historical armoury: one of the overlapping horizontal steel lames forming a defence for the lower back and buttocks, typically attached below the backplate of a cuirass.
"The diamond's large culet gave it an old-fashioned, candlelight-era sparkle."
"Under magnification the appraiser noted a slightly abraded culet on the antique cushion-cut diamond."
"The knight's harness included a finely articulated culet that flexed with every movement of his hips."
Regular plural; both the gemmological and armour senses pluralize normally.
"Most modern brilliant cuts have no culets at all, their pavilions meeting cleanly at a point."
The word for a diamond's bottom facet literally descends from the Latin word for 'buttocks' — jewellers have been calling it that since the days when old-cut gems were polished by candlelight.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of culet
The word entered English in the early seventeenth century, borrowed from French, where it derives from cul, meaning 'rump' or 'bottom', which itself goes back to the Latin culus of similar meaning. The same French root survives transparently in cul-de-sac, literally the 'bottom of the sack'. Both English senses reflect the root's anatomical literalism: the culet facet sits at the gem's 'backside', and the armour culet covers the wearer's own.
How culet is actually used
Both senses are technical terms used mainly by gemmologists, jewellers, and armour historians rather than in everyday speech. In gem grading reports the culet size may be described as 'none', 'small', 'medium', or 'large'; a visible culet is often considered undesirable in modern diamonds because it can look like a dark spot through the table. The armour sense is largely confined to museum catalogues and scholarship on medieval and Renaissance plate armour.
Easily confused with culet
A cutlet is a slice of meat or a breaded food portion, while a culet is either a flat facet at the base of a cut gemstone or a plate section of armour.