apples and oranges不表示苹果和橘子，那它到底指什么？

英语自学网

　　之前我们写过rain cats and dogs表示“倾盆大雨”，cats and dogs并不仅仅表示猫和狗，今天要写的apples and
oranges也是如此，并非苹果和橘子这么简单。
        　　apples and oranges是一个常用习语，表示“两者天差地别，无法比较;不能混为一谈”，它在美式英语中更为常见。
        　　The idiom, comparing apples and oranges, refers to the apparent differences
between items which are popularly thought to be incomparable or incommensurable,
such as apples and oranges.
        　　例如：
        　　You can't compare them. They are apples and oranges.
        　　你无法比较它们，它们完全不能混为一谈。