📚 AP Microeconomics Essential Vocabulary | AP微观经济备考核心词汇
Mastering AP Microeconomics requires a solid command of the discipline’s core terminology. The following guide breaks down the most important concepts into ten thematic sections, each pairing a clear English definition with an accurate Chinese explanation. Use these paired entries to strengthen your understanding and improve your performance on both multiple-choice and free-response questions.
掌握AP微观经济学需要牢固掌握学科核心术语。以下指南将最重要的概念分为十个主题，每个主题都提供清晰的英文定义与准确的中文解释配对呈现。利用这些双语条目加深理解，提升你在选择题和简答题中的表现。
1. Scarcity and Opportunity Cost | 稀缺性与机会成本
Scarcity is the fundamental economic problem: human wants are unlimited, but the resources needed to satisfy them are limited. Because of scarcity, individuals, firms, and governments must make choices and face trade-offs.
稀缺性是基本经济问题：人类的欲望是无限的，但满足这些欲望所需的资源是有限的。由于稀缺性，个人、企业和政府必须做出选择并面临权衡取舍。
Opportunity cost is the value of the next best alternative that must be given up when a decision is made. It includes both explicit costs (monetary payments) and implicit costs (the value of forgone time, resources, or income).
机会成本是做出决策时必须放弃的次优选择的价值。它包括显性成本（货币支出）和隐性成本（放弃的时间、资源或收入的价值）。
The Production Possibilities Curve (PPC) is a model that shows the maximum combinations of two goods an economy can produce given its resources and technology. Points inside the curve represent inefficiency, points on the curve are efficient, and points outside are unattainable with current resources. The slope of the PPC illustrates the opportunity cost of producing one more unit of a good.
生产可能性曲线（PPC）是一个模型，展示了一个经济体在给定资源和技术下能生产的两种商品的最大组合。曲线内的点代表无效率，曲线上的点是有效率的，曲线外的点在当前资源下无法达到。PPC的斜率说明了多生产一单位商品的机会成本。
2. Supply and Demand | 供给与需求
The law of demand states that, ceteris paribus, as the price of a good increases, the quantity demanded decreases, and vice versa. This inverse relationship is shown by a downward-sloping demand curve. A change in price causes a movement along the demand curve, while changes in non-price determinants (income, tastes, prices of related goods, expectations, number of buyers) shift the entire demand curve.
需求定律指出，在其他条件不变的情况下，商品价格上升，需求量下降，反之亦然。这种反向关系由向下倾斜的需求曲线表示。价格变化引起沿需求曲线的移动，而非价格决定因素（收入、偏好、相关商品价格、预期、买者数量）的变化会使整条需求曲线移动。
The law of supply states that, ceteris paribus, as the price of a good increases, the quantity supplied increases. This direct relationship is shown by an upward-sloping supply curve. Shifts in supply are caused by changes in input prices, technology, taxes and subsidies, expectations, the number of sellers, and weather conditions.
供给定律指出，在其他条件不变的情况下，商品价格上升，供给量增加。这种正向关系由向上倾斜的供给曲线表示。供给的移动由投入品价格、技术、税收与补贴、预期、卖者数量和天气状况等因素的变化引起。
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. At prices above equilibrium, a surplus (excess supply) exists, putting downward pressure on price. At prices below equilibrium, a shortage (excess demand) exists, pushing prices upward until equilibrium is restored.
市场均衡出现在需求量等于供给量的价格水平。价格高于均衡时存在过剩（超额供给），给价格带来下行压力。价格低于均衡时存在短缺（超额需求），推动价格上升直到恢复均衡。
3. Elasticity | 弹性
Price elasticity of demand (PED) measures how responsive quantity demanded is to a change in price. It is calculated as the percentage change in quantity demanded divided by the percentage change in price. Demand is elastic when |PED| > 1, unit elastic when |PED| = 1, and inelastic when |PED| < 1. Goods with close substitutes, luxuries, and those that take a large share of income tend to have more elastic demand.
需求的价格弹性（PED）衡量需求量对价格变化的反应程度。计算公式为需求量变动百分比除以价格变动百分比。当|PED| > 1时需求富有弹性，|PED| = 1时为单位弹性，|PED| < 1时缺乏弹性。有近似替代品、奢侈品和占收入比例大的商品需求往往更富有弹性。
PED = %ΔQd / %ΔP
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to price changes. It depends mainly on the ability and time producers have to adjust production.
供给的价格弹性（PES）衡量供给量对价格变化的反应程度，主要取决于生产者调整生产的能力和时间。
Cross-price elasticity of demand (XED) measures how the quantity demanded of one good responds to a price change of another good. Positive XED indicates substitute goods; negative XED indicates complementary goods.
需求的交叉价格弹性（XED）衡量一种商品的需求量对另一种商品价格变化的反应程度。正的XED表示替代品，负的XED表示互补品。
Income elasticity of demand (YED) measures how quantity demanded changes as consumer income changes. Normal goods have positive YED (YED > 1 for luxury goods, 0 < YED < 1 for necessities), and inferior goods have negative YED.
需求的收入弹性（YED）衡量需求量如何随消费者收入变化。正常品YED为正（奢侈品YED > 1，必需品0 < YED < 1），低档品YED为负。
4. Consumer Choice and Utility | 消费者选择与效用
Utility is the satisfaction a consumer derives from consuming a good or service. Total utility is the overall satisfaction from consuming a given quantity, while marginal utility is the additional satisfaction from consuming one more unit.
效用是消费者从消费商品或服务中获得的满足感。总效用是消费一定数量所获得的总满足程度，边际效用是额外消费一单位所带来的满足感增量。
The law of diminishing marginal utility states that as a consumer consumes more of a good, the additional satisfaction from each extra unit eventually decreases. Consumers maximize total utility when they allocate their budget so that the marginal utility per dollar spent is equal across all goods: MUx/Px = MUy/Py.
边际效用递减规律指出，随着消费者消费更多某种商品，每额外一单位带来的满足感最终会下降。消费者在所有商品上分配预算，使每元支出的边际效用相等时，总效用达到最大：MUx/Px = MUy/Py。
The budget constraint shows combinations of two goods a consumer can afford given income and prices. The slope of the budget line is -Px/Py. Changes in income shift the budget line parallelly, while changes in a good’s price rotate it.
预算约束表示在给定收入和价格下消费者能买得起的两种商品的组合。预算线的斜率为 -Px/Py。收入变化使预算线平移，一种商品的价格变化使预算线旋转。
The income effect and substitution effect explain the impact of a price change on quantity demanded. The substitution effect occurs when consumers buy more of a good that becomes relatively cheaper. The income effect reflects the change in purchasing power due to the price change. For a normal good, both effects work in the same direction; for an inferior good, they work in opposite directions.
收入效应和替代效应解释了价格变化对需求量的影响。替代效应指的是当一种商品相对变便宜时消费者会多买该商品。收入效应反映了价格变化带来的购买力变化。对于正常品，两种效应同向作用；对于低档品，两种效应反向作用。
5. Production and Costs | 生产与成本
The short run is a period in which at least one factor of production is fixed. The long run is a period long enough for all factors to become variable. Total product (TP) is the total output produced. Marginal product (MP) is the change in total product from hiring one more unit of a variable input.
短期是指至少一种生产要素固定不变的时期。长期是所有要素都可变的足够长的时期。总产量（TP）是生产的总产出。边际产量（MP）是增加一单位可变投入所带来的总产量变化。
The law of diminishing marginal returns states that in the short run, as more units of a variable input are added to a fixed input, the marginal product eventually decreases.
边际报酬递减规律指出，在短期中，随着越来越多的可变投入被添加到固定投入上，边际产量最终会下降。
Fixed costs (FC) do not vary with the level of output (e.g., rent). Variable costs (VC) change with output. Total cost (TC) = FC + VC. Average fixed cost (AFC) = FC / Q; average variable cost (AVC) = VC / Q; average total cost (ATC) = TC / Q. Marginal cost (MC) is the change in total cost from producing one more unit.
固定成本（FC）不随产量变化而变化（如租金）。可变成本（VC）随产量变化。总成本（TC）= FC + VC。平均固定成本（AFC）= FC / Q；平均可变成本（AVC）= VC / Q；平均总成本（ATC）= TC / Q。边际成本（MC）是增产一单位所带来的总成本变化。
In the long run, firms experience economies of scale when long-run average total cost falls as output increases. Diseconomies of scale occur when LRATC rises with output. Constant returns to scale describe the range where LRATC is flat.
在长期，当产量增加时长期平均总成本下降，企业经历规模经济。当LRATC随产量上升时出现规模不经济。规模报酬不变描述LRATC平坦的区间。
6. Perfect Competition | 完全竞争
Perfect competition is a market structure with many small firms, a homogeneous product, no barriers to entry or exit, and perfect information. Firms are price takers, meaning they must accept the market price and cannot influence it. The demand curve facing an individual firm is perfectly elastic (horizontal) at the market price.
完全竞争是一种市场结构，具有众多小企业、同质产品、无进入或退出壁垒以及完全信息。企业是价格接受者，即必须接受市场价格而无法影响它。单个企业面临的需求曲线在市场价格处是完全弹性的（水平线）。
In perfect competition, price equals marginal revenue (P = MR) and equals average revenue (AR). A profit-maximizing firm produces where MR = MC. In the short run, a firm can earn an economic profit, break even, or incur a loss. If P < AVC, the firm shuts down temporarily.
在完全竞争中，价格等于边际收益（P = MR）且等于平均收益（AR）。利润最大化的企业产量定在MR = MC处。短期内，企业可能获得经济利润、盈亏平衡或亏损。若P < AVC，企业暂时停产。
In the long run, economic profits attract new firms, shifting market supply to the right until P = minimum ATC and each firm earns zero economic profit. At this long-run equilibrium, firms achieve both allocative efficiency (P = MC) and productive efficiency (P = minimum ATC).
在长期，经济利润吸引新企业进入，市场供给右移，直到P = 最低ATC且每家企业获得零经济利润。在此长期均衡下，企业实现了配置效率（P = MC）和生产效率（P = 最低ATC）。
7. Monopoly | 垄断
A monopoly is a market structure with a single seller, a unique product with no close substitutes, and high barriers to entry. Barriers include legal restrictions, economies of scale, and control of essential resources. A monopolist is a price maker that faces a downward-sloping market demand curve.
垄断是一种只有单一卖者、产品独特且无近似替代品、进入壁垒高的市场结构。壁垒包括法律限制、规模经济和对关键资源的控制。垄断者是价格制定者，面临向下倾斜的市场需求曲线。
For a monopolist, marginal revenue lies below the demand curve because to sell an additional unit, the firm must lower the price on all previous units. The profit-maximizing quantity is found where MR = MC, and the price is read off the demand curve at that quantity. A monopoly produces a lower quantity and charges a higher price than a perfectly competitive market, creating a deadweight loss.
对垄断者而言，边际收益位于需求曲线下方，因为多卖一单位必须降低之前所有单位的价格。利润最大化产量在MR = MC处决定，价格则从该产量下的需求曲线读出。与完全竞争市场相比，垄断产量更低、价格更高，造成无谓损失。
Some monopolies practice price discrimination, charging different prices to different consumers for the same good, based on willingness to pay. Perfect price discrimination can eliminate deadweight loss by converting all consumer surplus into producer surplus.
一些垄断企业实行价格歧视，根据支付意愿对同一商品向不同消费者收取不同价格。完全价格歧视可以将全部消费者剩余转化为生产者剩余，从而消除无谓损失。
A natural monopoly arises when economies of scale are so large that a single firm can supply the entire market at a lower average total cost than two or more firms. Governments often regulate natural monopolies through price ceilings (average-cost pricing or marginal-cost pricing with subsidies).
自然垄断出现在规模经济如此之大，以至于单一企业能以比两家或多家企业更低的平均总成本供应整个市场。政府通常通过价格上限（平均成本定价或边际成本定价加补贴）来管制自然垄断。
8. Monopolistic Competition and Oligopoly | 垄断竞争与寡头
Monopolistic competition features many firms, differentiated products, few barriers to entry, and some price-making ability. In the short run, firms can earn profits like a monopoly. In the long run, entry shifts demand and marginal revenue left until P = ATC and economic profit is zero, but the firm still produces where P > MC, leading to excess capacity and no allocative efficiency.
垄断竞争具有很多企业、产品差异化、进入壁垒少和一定的定价能力等特点。短期企业可以像垄断者一样盈利。长期中，进入使需求和边际收益左移，直到P = ATC，经济利润为零，但企业仍在P > MC处生产，导致产能过剩且未实现配置效率。
An oligopoly is a market dominated by a few large firms. Firms are interdependent, meaning each firm’s actions affect rivals. Strategic behavior is analyzed using game theory. A dominant strategy is one that is best for a player regardless of the other player’s choice. Nash equilibrium occurs when each player chooses their best strategy given the strategies chosen by others.
寡头是由少数大企业主导的市场。企业间相互依存，即每个企业的行为会影响对手。战略行为用博弈论分析。无论对方如何选择，对自己都是最佳的策略称为占优策略。纳什均衡出现在每个参与者均基于他人策略选择自身最优策略的情况下。
Oligopolistic markets can exhibit a kinked demand curve, where the demand is more elastic above the current price and less elastic below it, leading to price rigidity. Collusion occurs when firms cooperate to act like a monopoly and maximize joint profits. A cartel is a formal agreement to collude, which is illegal in many countries.
寡头市场可能出现弯折的需求曲线，在现行价格上方需求弹性较大，下方弹性较小，从而导致价格刚性。合谋是指企业合作像垄断者一样行动以最大化共同利润。卡特尔是正式合谋协议，在许多国家是非法的。
9. Factor Markets | 要素市场
Factor markets are where firms purchase the inputs needed for production—labour, land, capital, and entrepreneurship. The demand for factors is a derived demand, meaning it arises from the demand for the final goods and services the factors help produce.
要素市场是企业购买生产所需投入品——劳动、土地、资本和企业家才能——的市场。对要素的需求是派生需求，即源于对要素所帮助生产的最终产品与服务的需求。
Marginal revenue product (MRP) measures the additional revenue generated by hiring one more unit of a factor. For labour, MRP = MPL × MR. A profit-maximizing firm hires the quantity of labour where MRP = wage rate.
边际收益产品（MRP）衡量多雇佣一单位要素所带来的额外收益。对劳动而言，MRP = MPL × MR。利润最大化企业雇佣劳动的数量确定在MRP = 工资率处。
In a perfectly competitive labour market, many firms and workers interact, and the wage is set by market supply and demand. A single firm hires workers where MRP = market wage. In a monopsony, a single firm is the dominant buyer of labour. It faces an upward-sloping market labour supply curve and has marginal factor cost (MFC) above the supply. A monopsonist hires fewer workers and pays a lower wage than a competitive market, generating inefficiency.
在完全竞争劳动市场中，众多企业和工人相互作用，工资由市场供求决定。单个企业按MRP = 市场工资来雇佣工人。在买方垄断（monopsony）中，单一企业是劳动的主要购买者。它面临向上倾斜的市场劳动供给曲线，边际要素成本（MFC）高于供给曲线。买方垄断者雇佣更少的工人，支付更低的工资，导致无效率。
10. Market Failure and the Role of Government | 市场失灵与政府角色
Market failure occurs when the free market fails to allocate resources efficiently. Externalities are costs or benefits that affect third parties not directly involved in a transaction. A negative externality (e.g., pollution) leads to overproduction because the market ignores external costs. A positive externality (e.g., education) leads to underproduction because the market ignores external benefits.
市场失灵发生在自由市场未能有效配置资源时。外部性是指影响未直接参与交易的第三方的成本或收益。负外部性（如污染）导致生产过剩，因为市场忽略了外部成本。正外部性（如教育）导致生产不足，因为市场忽略了外部收益。
Public goods are non-rival (one person’s consumption does not reduce availability to others) and non-excludable (people cannot be prevented from using the good). Examples include national defence and street lighting. The free-rider problem causes private markets to underprovide public goods, creating a rationale for government provision.
公共物品具有非竞争性（一人消费不会减少他人可用的数量）和非排他性（无法阻止他人使用）。例子包括国防和路灯。搭便车问题导致私人市场提供公共物品不足，这为政府提供创造了理由。
Common resources are rival but non-excludable, such as fisheries or clean air. They tend to be overused, a problem known as the tragedy of the commons. Government interventions include taxes, subsidies, tradable pollution permits, price ceilings, price floors, and regulations to correct market failures and improve social welfare.
公共资源具有竞争性但非排他性，如渔场或清洁空气。它们往往被过度使用，这被称为公地悲剧。政府干预措施包括税收、补贴、可交易污染许可证、价格上限、价格下限以及法规，以纠正市场失灵并提高社会福利。
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