1
a [number]-carat [gemstone]
用作前置定语时，数字与 carat 之间用连字符，且 carat 用单数。
She bought a two-carat diamond for the ring.
她为戒指买了一颗两克拉的钻石。
克拉
carats — plural of carat
先理解核心含义，再看它在真实句子里的用法。
克拉
carat
She bought a two-carat diamond for the ring.
她为戒指买了一颗两克拉的钻石。
一种质量单位,等于200毫克,主要用于测量宝石和珍珠。
A metric unit of mass equal to exactly 200 mg, chiefly used for measuring precious stones and pearls.
用于衡量黄金纯度的24分制标度。
A 24-point scale used to measure the purity of gold.
The jeweler weighed the loose stone and found it to be nearly two carats.
珠宝商称了这颗裸石，发现它差不多有两克拉。
Each carat of this sapphire adds hundreds of dollars to the price.
这种蓝宝石每克拉都会让价格增加几百美元。
She saved for months to buy a bracelet with three carats of diamonds.
她攒了几个月的钱，才买下一条镶有三克拉钻石的手链。
用作前置定语时，数字与 carat 之间用连字符，且 carat 用单数。
She bought a two-carat diamond for the ring.
她为戒指买了一颗两克拉的钻石。
carat 是可数名词，表示重量时复数加 -s。
This emerald weighs five carats.
这颗祖母绿重五克拉。
Not this
The diamond weighs two carat.
Use this
The diamond weighs two carats.
carat 是可数名词，复数形式是 carats；数词大于 1 时要用复数。汉语名词没有复数变化，所以容易漏掉 -s。
Not this
She bought a two carats diamond.
Use this
She bought a two-carat diamond.
“数词 + 单位名词”放在名词前作定语时，单位名词要用单数，并用连字符构成复合形容词（two-carat），不能写成 two carats。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
克拉重量
The carat weight of the diamond is clearly stated on the certificate.
钻石的克拉重量在证书上有明确标注。
一克拉钻石
She chose a one-carat diamond for her engagement ring.
她为订婚戒指选了一颗一克拉的钻石。
半克拉
A half carat is enough if the stone is well cut.
如果切工好，半克拉就够了。
每克拉
The price per carat rises sharply for larger stones.
大颗宝石的每克拉价格会急剧上涨。
两克拉的宝石
He inherited a two-carat stone from his grandmother.
他从祖母那里继承了一颗两克拉的宝石。
十足的；地地道道的
He’s a 24-carat fool.
他是个十足的大傻瓜。
Use carats naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
carat 与 carrot 同音；胡萝卜(carrot)多一个 r 所以更重，少一个 r 的 carat 是钻石重量单位('克拉')。
语域：neutral 常见场景：jewelry retail、gemological reports、diamond grading carat 是宝石（尤其是钻石）重量的标准单位，多在珠宝交易、鉴定书和日常谈钻石大小等场合出现。它通常属于中性/正式用法，但口语中也很自然，没有明显的随意色彩。
carat rhymes with carrot, caret, parrot, and karat, all ending in the unstressed /ət/ after /r/. Beware lookalikes with different sounds: 'car' is /kɑːr/, 'career' is /kəˈrɪr/, and 'crate' is /kreɪt/.
Dictionary facts from ECDICT, WIKTIONARY.