carat

American  

[kar-uht] / ˈkær ət /

noun

1. a unit of weight in gemstones, 200 milligrams (about 3 grains of troy or avoirdupois weight). c., ct.

2. karat.

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carat British  

/ ˈkærət /

noun

1. a measure of the weight of precious stones, esp diamonds. It was formerly defined as 3.17 grains, but the international carat is now standardized as 0.20 grams

2. Usual US spelling: karat.  a measure of the proportion of gold in an alloy, expressed as the number of parts of gold in 24 parts of the alloy

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Etymology

Origin of carat

1545–55; < Medieval Latin carratus (used by alchemists) < Arabic qīrāṭ weight of 4 grains < Greek kerátion carob bean, weight of 3.333 grains, literally, little horn, equivalent to kerat- (stem of kéras ) horn + -ion diminutive suffix

Explanation

Precious jewels are measured in carats instead of ounces or grams. If your sister gets a three-carat diamond ring, she's getting a ring that weighs 600mg, which is big enough to be called "a rock." A variant of carat is karat. The former is usually used with diamonds and is a measure of weight, whereas the latter is usually used for gold and is a measure of purity. One karat is 1/24th of the mass, so 24-karat gold is pure. An 18-karat gold ring is 18/24 (or 3/4) gold and 6/24 (or 1/4) other metals.

Example Sentences

It’s not something I had even considered while I was worrying about the cut, carat, clarity and color.

From MarketWatch • Feb. 3, 2026

Rough diamonds were expected to fetch $99.3 per carat, down from $128.8 in 2024, it said.

From Barron's • Jan. 21, 2026

A harbinger of disaster is a replica of the harness-like 2,842 carat necklace from the “Diamond Necklace Affair” of 1785.

From The Wall Street Journal • Jan. 8, 2026

The internet hummed with commentary, memes, and close analysis of carat weight.

From Salon • Aug. 31, 2025

On his palm rested a two- carat diamond and a partial denture.

From "Slaughterhouse-Five" by Kurt Vonnegut