📚 AS CCEA Economics: Quick Memorisation Guide for Key Terms | AS CCEA 经济学：核心术语速记指南
Mastering key economic terms is essential for success in AS CCEA Economics. This guide provides clear definitions paired with Chinese translations, breaking down core concepts across micro and macro topics. Use this to strengthen your vocabulary and exam technique.
掌握关键经济学术语是成功通过 AS CCEA 经济学考试的基础。本指南提供清晰的定义并配以中文翻译，分解微观与宏观核心概念。使用本指南强化您的词汇和考试技巧。
1. Scarcity, Choice & Opportunity Cost | 稀缺性、选择与机会成本
Scarcity is the fundamental economic problem: it arises because human wants are unlimited, yet the resources available to satisfy them are limited. This forces individuals, firms and governments to make choices.
稀缺性是基本的经济问题：它产生是因为人类的欲望是无限的，但满足这些欲望的资源是有限的。这迫使个人、企业和政府做出选择。
Opportunity cost is defined as the next best alternative foregone whenever a choice is made. For example, if a government decides to spend more on healthcare, the opportunity cost might be fewer resources available for education.
机会成本被定义为每当做出一种选择时所放弃的次优选项。例如，如果政府决定在医疗上投入更多，机会成本可能是可用于教育的资源减少。
The factors of production are the inputs used to produce goods and services. They are commonly classified as land (natural resources), labour (human effort), capital (man-made aids to production) and enterprise (the willingness to take risks and organise the other factors).
生产要素是用于生产商品和服务的投入。它们通常分为土地（自然资源）、劳动力（人的努力）、资本（人为生产辅助工具）和企业精神（承担风险并组织其他要素的意愿）。
A Production Possibility Frontier (PPF) shows the maximum combinations of two goods an economy can produce when all resources are fully and efficiently employed. Points inside the PPF represent inefficiency; shifts outward indicate economic growth.
生产可能性边界（PPF）显示了一个经济体在资源被充分利用和有效率使用时能够生产的两种商品的最大组合。边界内的点代表效率低下；边界外移表示经济增长。
2. Demand & Supply | 需求与供给
Demand refers to the quantity of a good or service that consumers are willing and able to purchase at various prices over a given period. The law of demand states there is an inverse relationship between price and quantity demanded, ceteris paribus. A movement along the demand curve is caused solely by a change in price.
需求是指消费者在一定时期内愿意并且能够以各种价格购买的商品或服务的数量。需求定律指出，在其他条件不变的情况下，价格与需求量之间存在反向关系。需求曲线上的滑动完全由价格变动引起。
Shifts of the demand curve are caused by non-price factors. These include changes in real income, tastes and preferences, the prices of substitute or complementary goods, population size and expectations about future prices. For instance, an increase in consumer income will shift the demand curve for normal goods to the right.
需求曲线的移动由非价格因素引起。这些因素包括实际收入的变化、口味和偏好、替代品或互补品的价格、人口规模以及对未来价格的预期。例如，消费者收入的增加会使正常商品的需求曲线向右移动。
Supply is the quantity of a good that producers are willing and able to offer for sale at different prices. The law of supply indicates a positive relationship between price and quantity supplied. A rise in price provides an incentive to produce more.
供给是生产者愿意并且能够以不同价格出售的商品数量。供给定律表明价格与供给量之间存在正向关系。价格上涨激励生产者生产更多。
Supply curve shifts occur when there are changes in conditions of production. Key shift factors include changes in the costs of raw materials or labour, advances in technology, indirect taxes and subsidies, the number of sellers, and weather conditions for agricultural goods. A subsidy lowers production costs and shifts the supply curve to the right.
当生产条件改变时，供给曲线发生移动。关键的移动因素包括原材料或劳动力成本的变化、技术进步、间接税和补贴、卖家的数量以及农产品的天气条件。补贴降低了生产成本并使供给曲线向右移动。
3. Elasticities: PED, YED, XED & PES | 弹性：需求价格弹性、收入弹性、交叉弹性与供给价格弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in price. The formula is:
需求价格弹性（PED）衡量需求量对价格变动的反应程度。公式为：
PED = %ΔQd / %ΔP
If PED > 1, demand is price elastic; consumers are very responsive to price changes. If PED < 1, demand is price inelastic. If PED = 1, demand is unitary elastic. A perfectly inelastic demand curve is vertical (PED = 0), and a perfectly elastic demand curve is horizontal (PED = ∞).
如果PED > 1，需求是富有弹性的；消费者对价格变化非常敏感。如果PED < 1，需求缺乏弹性。如果PED = 1，需求为单位弹性。完全无弹性的需求曲线是垂直的（PED = 0），完全有弹性的需求曲线是水平的（PED = ∞）。
Factors determining PED include the availability of close substitutes, whether a good is a necessity or a luxury, the proportion of income spent on the good, and the time period considered. Goods with many substitutes tend to have more elastic demand.
决定PED的因素包括相近替代品的可获得性、商品是必需品还是奢侈品、花费在该商品上的收入比例以及所考虑的时间长度。存在许多替代品的商品往往需求弹性更大。
Income elasticity of demand (YED) measures the responsiveness of demand to a change in consumer income:
需求收入弹性（YED）衡量需求对消费者收入变化的反应程度：
YED = %ΔQd / %ΔY
Normal goods have a positive YED; as income rises, demand increases. Inferior goods have a negative YED. Among normal goods, those with YED > 1 are luxury goods, while those with 0 < YED < 1 are necessities.
正常商品具有正的YED；收入上升时需求增加。劣质商品具有负的YED。在正常商品中，YED > 1的是奢侈品，0 < YED < 1的是必需品。
Cross elasticity of demand (XED) measures the responsiveness of demand for one good (A) to a change in the price of another good (B):
需求交叉弹性（XED）衡量一种商品（A）的需求对另一种商品（B）价格变化的反应程度：
XED = %ΔQdA / %ΔPB
XED is positive for substitute goods (e.g. tea and coffee) and negative for complementary goods (e.g. printers and ink cartridges). The larger the magnitude, the stronger the relationship.
对于替代品（如茶和咖啡），XED为正；对互补品（如打印机和墨盒），XED为负。数值的大小表示关系的强弱。
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to a price change:
供给价格弹性（PES）衡量供给量对价格变动的反应程度：
PES = %ΔQs / %ΔP
The main determinants of PES are the time period and the level of spare capacity. Supply is more elastic in the long run because firms can adjust all factors of production. If a firm has plenty of spare capacity, supply can be more responsive.
PES的主要决定因素是时间长度和剩余产能的大小。长期内供给更具弹性，因为企业可以调整所有生产要素。如果企业有大量闲置产能，供给反应可能更迅速。
4. Market Equilibrium & Government Intervention | 市场均衡与政府干预
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. At this point, there is no tendency for change. Any price above equilibrium will create excess supply (a surplus), pushing price down. Any price below equilibrium will generate excess demand (a shortage), driving price up.
市场均衡出现在需求量等于供给量的价格水平上。在这一点上，没有变化的趋势。任何高于均衡的价格都会产生超额供给（过剩），使价格下降。任何低于均衡的价格都会产生超额需求（短缺），推动价格上升。
Governments intervene in markets to correct perceived imbalances or to achieve social objectives. A maximum price (price ceiling) is set below the free-market equilibrium to make goods more affordable, but this often leads to persistent shortages and secondary markets.
政府干预市场以纠正感知到的失衡或实现社会目标。最高限价（价格上限）定在自由市场均衡以下，使商品更便宜，但这通常导致持续的短缺和黑市。
A minimum price (price floor) is set above equilibrium to support producers’ incomes, causing excess supply that may require government purchases of the surplus. Examples include agricultural price supports and minimum wages in labour markets.
最低保护价（价格下限）定在均衡以上以支持生产者的收入，导致超额供给，这可能需要政府购买剩余产品。例子包括农产品价格支持和劳动力市场的最低工资。
Indirect taxes (e.g. VAT, excise duties) increase production costs and shift the supply curve leftwards, raising the equilibrium price and reducing quantity. The burden of taxation (incidence) is shared between consumers and producers, depending on relative elasticities.
间接税（如增值税、消费税）增加生产成本并使供给曲线向左移动，提高了均衡价格，减少了均衡数量。税收负担（归宿）由消费者和生产者共同承担，其分配取决于相对弹性。
Subsidies lower production costs, shifting the supply curve rightwards. This reduces the market price and encourages higher output. Governments use subsidies to support socially desirable goods or protect domestic industries.
补贴降低了生产成本，使供给曲线向右移动。这降低了市场价格并鼓励增加产出。政府用补贴来支持对社会有益的商品或保护国内产业。
5. Costs, Revenues & Profit Maximisation | 成本、收入与利润最大化
In the short run, at least one factor of production is fixed. In the long run, all factors are variable. The distinction is crucial for understanding cost behaviour. Fixed costs (FC) do not vary with output, while variable costs (VC) change directly with production levels. Total cost (TC) = FC + VC.
在短期内，至少有一种生产要素是固定的。在长期内，所有要素都是可变的。这一区分对于理解成本行为至关重要。固定成本（FC）不随产量变化，而可变成本（VC）直接随产量变化。总成本 (TC) = FC + VC。
Average cost (AC) is TC ÷ output. Marginal cost (MC) is the change in total cost from producing one additional unit: MC = ΔTC / ΔQ. The law of diminishing marginal returns states that as more of a variable factor is added to a fixed factor, the extra output produced will eventually fall, causing MC to rise.
平均成本（AC）是总成本除以产量。边际成本（MC）是多生产一单位产品所带来的总成本变化：MC = ΔTC / ΔQ。边际收益递减规律指出，当可变要素不断增加地投入到固定要素中时，额外产出最终会下降，导致MC上升。
Economies of scale refer to the fall in long-run average costs as output expands. Sources include purchasing economies, technical economies, financial economies and managerial specialisation. Diseconomies of scale occur when the firm becomes too large, causing average costs to rise due to coordination and communication problems.
规模经济指的是随着产出扩大，长期平均成本下降。来源包括采购经济、技术经济、金融经济和管理专业化。规模不经济发生在企业变得过于庞大时，由于协调和沟通问题导致平均成本上升。
Total revenue (TR) = Price × Quantity. Average revenue (AR) = TR ÷ Q = Price. Marginal revenue (MR) is the change in total revenue from selling one more unit. A rational firm aims to maximise profit, which occurs where the difference between TR and TC is greatest. This is mathematically equivalent to producing where MC = MR, provided that price covers average variable cost.
总收入 (TR) = 价格 × 数量。平均收入 (AR) = TR ÷ Q = 价格。边际收入 (MR) 是销售额外一单位产品所带来的总收入变化。理性的企业追求利润最大化，这发生在TR与TC之差最大的地方。数学上这等价于在MC = MR处生产，前提是价格能够覆盖平均可变成本。
6. Market Structures | 市场结构
Perfect competition is a theoretical market structure characterised by many small firms, a homogeneous product, no barriers to entry or exit, and perfect knowledge. Firms are price takers and can earn only normal profits in the long run. Output is where P = MC, leading to allocative efficiency.
完全竞争是一种理论上的市场结构，其特征是众多小企业、同质化产品、无进入或退出壁垒和完全信息。企业是价格接受者，在长期只可赚取正常利润。产出在P = MC处，达到分配效率。
Monopoly exists when a single firm dominates the market. High barriers to entry (legal, technological, or strategic) protect its position. The monopolist is a price maker and can earn supernormal profits even in the long run. Output is where MC = MR, but price is set above MC, causing allocative inefficiency.
垄断存在于一家企业主导市场的情形。高进入壁垒（法律、技术或策略性）保护其地位。垄断者是价格制定者，甚至在长期也能赚取超额利润。产出在MC = MR处，但价格设定在MC之上，造成分配无效率。
Monopolistic competition features many firms selling differentiated products, giving them some degree of price-making power. Low barriers allow for easy entry. In the long run, new entrants compete away supernormal profits, and firms end up with normal profits but excess capacity.
垄断竞争的特点是许多企业销售差异化产品，从而获得一定的定价权。低壁垒允许容易进入。在长期，新进入者会竞相消除超额利润，企业最终获得正常利润但存在过剩产能。
Oligopoly is a market dominated by a few large firms, where barriers to entry are substantial. Firms are interdependent, meaning the actions of one firm influence rivals’ behaviour. This often leads to non-price competition, price rigidity, and the potential for collusion to act like a monopoly.
寡头市场是由少数几家大企业主导的市场，进入壁垒很高。企业之间相互依赖，意味着一个企业的行为会影响竞争对手的决策。这常常导致非价格竞争、价格粘性以及可能串通起来像垄断者一样行动。
7. Market Failure & Externalities | 市场失灵与外部性
Market failure occurs when the free market mechanism leads to a misallocation of resources, failing to achieve the socially optimal level of output. It can arise from externalities, public goods, merit and demerit goods, information failures and market power.
市场失灵发生在自由市场机制导致资源错配，未能实现社会最优产出水平的时候。它可能由外部性、公共物品、有益品和有害品、信息失灵以及市场势力引起。
An externality is a cost or benefit imposed on a third party not directly involved in the transaction. Negative production externalities (e.g. factory pollution) lead to overproduction because private costs are lower than social costs. Negative consumption externalities (e.g. passive smoking) also result in overconsumption.
外部性是施加于未直接参与交易的第三方的成本或收益。负生产外部性（如工厂污染）导致过度生产，因为私人成本低于社会成本。负消费外部性（如被动吸烟）也导致过度消费。
Positive externalities generate social benefits greater than private benefits. Positive consumption externalities (e.g. vaccinations) cause underconsumption. Positive production externalities (e.g. research spillovers) lead to underproduction. Markets fail to provide the socially optimal level of these goods.
正外部性产生的社会收益大于私人收益。正消费外部性（如疫苗接种）导致消费不足。正生产外部性（如研发溢出效应）导致生产不足。市场无法提供这类商品的社会最优水平。
Public goods are non-excludable (you cannot stop people from using them) and non-rival (one person’s use does not reduce availability for others). Examples include national defence and street lighting. The free-rider problem makes private provision unprofitable, so the government usually steps in to provide them.
公共物品具有非
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