arithmetic/ə'rɪθmətɪk/

n.

➊ the part of mathematics that involves the adding and multiplying, etc. of numbers

➋ the act or process of calculating a number

n. [U]

➊ 算术：an arithmetic test 算术测验

◇He is good at arithmetic. 他算术很好。

➋ 算术运算：

◇These kids have had seven years in school and they can't even do some simple arithmetic! 这些孩子已经上了7年学了，他们竟然连一些简单的算术也不会做。

巧记 arithmetic后面无s，但mathematics是以s结尾的。