Definition

1. Noun:
   • A unit of measurement for the purity of gold: A carat (abbreviated as 'kt' or 'K') indicates the proportion of pure gold in an alloy, with pure gold defined as 24 carats. For example, 18-karat gold is 75% pure gold.
   • A unit of mass for gemstones: A metric carat is a standard unit of weight equal to 200 milligrams (0.2 grams), used specifically for measuring diamonds and other precious stones.

Examples of Usage

• For gold purity:
  • This ring is made of 22-carat gold. (This means the gold alloy is 22/24 parts pure gold.)
  • Pure gold is 24 carats.
• For gemstone weight:
  • The diamond weighs 1.5 carats.
  • Large gemstones over 5 carats are very rare.

Advanced Usage

• "Karat" vs. "Carat": In American English, 'karat' (abbreviation 'K') is typically used for gold purity, while 'carat' (abbreviation 'ct') is used for gemstone weight. In British English, 'carat' can be used for both.
  • She prefers 18-karat gold jewelry. (Referring to purity)
  • The sapphire is a two-carat stone. (Referring to weight)

Variants and Related Words

• Karat (n): The American English spelling specifically for the unit of gold purity.
• Caratage (n): A less common term referring to the carat purity of gold.
• Carat weight (n): The weight of a gemstone measured in carats.

Synonyms

• For gold purity: Fineness (expressed differently, e.g., .750).
• For gem weight: Unit of mass (specific to gems; no direct synonym).

Related Phrases and Idioms

• "Solid gold": Often implies high caratage, like 18K or above.
  • The bracelet is solid 18-carat gold.
• "A carat or more": A phrase used in the gem trade to indicate a minimum desirable size.
  • Many buyers look for diamonds of a carat or more.

Noun

1. the unit of measurement for the proportion of gold in an alloy; 18-karat gold is 75% gold; 24-karat gold is pure gold
2. a unit of weight for precious stones = 200 mg