Bread and butter 这个组合除了有面包黄油的意思外，我们可以用它来指某人的谋生之道，生计或主要收入来源。
- You can't ask your neighbour to fix your car for free. He's a mechanic and fixing cars is his bread and butter.
- Mary was very helpful to her clients. She knew they were her bread and butter.
值得注意的是，另一个含有 butter 的短语是 to butter up，意思是拍人马屁。
- Fred was new to the company but he didn't waste time before buttering up the boss.
