apples and oranges是一个常用习语，根据其英英释义to compare things that are very different，表示“风马牛不相及的事物;天差地别的事物”，它在美式口语中十分常见。

【例句】
You can't compare your job as a doctor to mine as a musician—that's comparing apples and oranges! 　　
你是位医生，我是位音乐家，你没法比较咱俩的工作，因为它们风马牛不相及。

They really are apples and oranges.
他们确实是迥然不同。