物质名词（通常为不可数，但表示不同种类时可用复数或与 a 或 an 连用，例如 The shop sells several different breads 中的 bread）a noun that is usually uncountable but can be made plural or used with or when you are talking about different types of sth. For example,bread is used as a mass noun inthe shop sells several different breads .