A1 used before a noun to refer to a single thing or person that has not been mentioned before, especially when you are not referring to a particular thing or person一（个）（用于名词前，表示未曾提及的，尤其是非特指的人、事、物）

A1 used to say what type of thing or person something or someone is（表示人或物的类型）

A1 used to mean any or every thing or person of the type you are referring to（泛指所指类别中的任何一个）

used before some uncountable nouns when you want to limit their meaning in some way, such as when describing them more completely or referring to one example of them（用于一些不可数名词前，在某种意义上起限定性作用）

A2 used before some nouns of action when referring to one example of the action（用于某些行为名词前）一下；一次

A2 used when referring to a unit or container of something, especially something you eat or drink（尤指饮食的）一份

A2 used before the first but not the second of two nouns that are referred to as one unit（用于被视为一体的两个名词中的第一个词前）一副；一套；一组

A2 used before some words that express a number or amount（用于某些表示数量的词前）

used in front of a person's name when referring to someone who you do not know（用于不认识的人名前）有个，某一（个）

used in front of someone's family name when they are a member of that family（用于某人的姓之前，表示其为该姓家族成员）

used before the name of a day or month to refer to one example of it（用于日期、月份前）一个

A1 one一

A2 used between a fraction and a unit of measurement（用于分数和度量单位之间）

A2 used when saying how often something happens in a certain period（指某事在特定时间段内发生的频率）每一（个），一

A2 used when saying how much someone earns or how much something costs in a certain period（指特定时间段内的收入或费用）一，每

written abbreviation foramp noun(ELECTRICITY) 安（电流强度单位amp“安培”的缩写）