A thin layer on the surface of a solid or a liquid that is differentiated in some way from the underlying bulk material.
Mid 19th century; earliest use found in Hugh Miller (1802–1856), geologist, evangelical journalist, and writer.
英汉双解词典包含464360条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。