customs
美 ['kʌstəmz]
n. 海关；风俗（custom的复数）；习惯；关税
customs clearance 海关放行；结关
customs declaration 报关单；申报关税
customs officer 海关官员
customs office 海关
customs house n. 海关
They assumed the customs of their new country.他们采用他们新来到国家的习俗。
For years he has been smuggling watches through customs.
多年来他一直夹带手表过海关。

custom什么时候用复数

风俗习俗，统称时可用。
Customs 特指海关