Most Economics confusion comes from a handful of near-twin terms. The two words look alike, the diagram looks alike, and the answer changes completely. This page gives each term in plain language, an original example, the term it is most confused with, and the lesson that teaches it.
Use it as a reference, and confirm exact definitions against your own syllabus. The English, Malay and Chinese concept bridge lets you look up a term in all three languages with contextual sentences.
Core ideas
1. Scarcity. Resources are limited compared with wants, so choices must be made. Example: a school canteen has one freezer, so it cannot stock every frozen drink. Confused with: shortage, which is a market gap at one price. See scarcity, choice and opportunity cost.
2. Opportunity cost. The value of the next most valued alternative you give up. Example: Farid spends Saturday afternoon at a paid job instead of playing football. His opportunity cost is the football, not the pay. Confused with: total cost of everything given up. Practise in identify the next most valued alternative.
3. Want and effective demand. A want is a wish. Effective demand is a want backed by the ability to pay. Example: Aisha wants a new laptop, but only has effective demand once she has the money. See want versus effective demand.
4. Capital. In economics, capital means man-made goods used to produce other goods, such as machines. Example: a baker’s oven. Confused with: money capital, or “capital” in accounting, which can mean funds put in by owners. Check the context of the question.
Demand and supply
5. Demand and quantity demanded. Demand is the whole relationship between price and quantity. Quantity demanded is one point on it. Example: at RM5 buyers want 200 cups a day, and that 200 is a quantity demanded. See movement along demand versus a shift.
6. Movement and shift. A change in price moves you along a curve. A change in another factor, such as tastes or income, shifts the whole curve. The help page confusing a shift with a movement works through it.
7. Supply and quantity supplied. The same split as demand. Example: a rise in the cost of flour shifts the supply of bread, but a rise in the price of bread only extends the quantity supplied. See supply shift versus price response.
8. Equilibrium. The price where quantity demanded equals quantity supplied. Example: at RM4, buyers want 60 and sellers offer 60. Confused with: the price anyone likes. Practise with finding an equilibrium.
9. Shortage and surplus. A shortage is demand above supply at a price, and a surplus is supply above demand. Example: at RM6, sellers offer 100 but buyers want 40, so there is a surplus of 60. See shortage and price adjustment.
Elasticity and money
10. Price elasticity of demand (PED). How responsive quantity demanded is to a price change, measured as %Δ quantity ÷ %Δ price. Example: price up 10%, quantity down 15%, so PED is −1.5. The elasticity module explains the sign.
11. Elastic and inelastic. Elastic means the response is more than proportional (size above 1). Inelastic means less (size below 1). Confused with: steep and flat graph shapes, which depend on the scale. See interpreting an elasticity value.
12. Revenue and profit. Revenue is price times quantity sold. Profit is revenue minus total cost. Example: 50 items at RM8 gives RM400 revenue, and with RM300 costs the profit is RM100. See elasticity and revenue and firms, costs and scale.
13. Nominal and real. A nominal value is measured at current prices. A real value is adjusted for price changes. Example: wages up 4% while prices rise 5% means real wages fell. See inflation and unemployment.
Markets and the economy
14. Private and social cost. Private cost falls on the buyer or seller. Social cost adds costs to others, such as noise or pollution. Example: a factory’s fuel bill is private, its smoke is an external cost. See market failure concepts.
15. Tax and subsidy. A tax is a payment to government that raises a seller’s cost. A subsidy is a payment to a producer that lowers it. Both shift a supply curve in opposite directions. See public finance.
16. Appreciation and depreciation. A currency appreciates when it buys more of another currency, and depreciates when it buys less. Example: if RM1 buys fewer US dollars than last month, the ringgit has depreciated. See trade and exchange rates.
How to learn a confusing pair
Take one pair and write two short sentences, one for each word, about a fictional product. Change one fact and decide which term the sentence now needs. Put the pair in your mistake log if you ever mix it up.
Return to the Economics learning guide for the topic map. If you want a teacher to test your understanding aloud, online one-to-one Economics tuition is worth considering.