前两个词的外形易混：costume意为“衣服，服装”，尤其是指一个时代或一个民族所穿的服装，而custom则是指“一种传统习俗”。customs的复数除作“习俗”解外，还可作“海关(常须大写)，关税”解。

• The girls were wearing their national costume(s) .
  这些姑娘们穿着自己的民族服装。
• A lot of the old customs are dying out now.
  许多旧的习俗正在消失。
• It took us only four minutes to get through the Customs .
  我们只用了四分钟就通过了海关。
• Customs are taxes paid to the government on goods brought in from foreign countries.
  关税是就从外国带入的物品向政府缴纳的税。