There are restrictions on how many goods you can bring into the country.

restrictions 是名词 restriction 的复数形式，来自动词 restrict（限制、约束），指"限制规定"或"约束条件"。前缀 re- 表示"再次"，词根 strict 来自拉丁语 strictus（收紧的），所以 restriction 字面意思是"再次收紧"，引申为"限制"。