13

易错句子She bought threeteen eggs at the market.→正确表达She bought thirteen eggs at the market.

13 的英文是 thirteen，词干是 thir-（与 third 同源），不是 three-；受 three 影响写成 threeteen 或 thirtheen 都属拼写错误，正确形式只有 thirteen。

易错句子My office is on the thirteen floor.→正确表达My office is on the thirteenth floor.

表示楼层、次序要用序数词，13 的序数词是 thirteenth（缩写 13th），基数词 thirteen 不能直接修饰 floor；汉语“十三楼”没有词形变化，所以容易漏掉 -th。

易错句子He is a thirteen-years-old boy.→正确表达He is a thirteen-year-old boy.

“数词+名词+形容词”作前置定语构成复合形容词时，中间名词要用单数并加连字符，写成 thirteen-year-old，不能保留复数 -s。