Economic and Business Environment · Basics of Demand and Supply and Forms of Market Competition

Meaning and Law of Demand for CSEET

Updated 11 October 2026 · Fact-checked

Demand is the quantity of a good a consumer is willing and able to buy at a given price in a given time. The law of demand says that, other things remaining equal, when price falls, quantity demanded rises, and when price rises, it falls. The demand curve therefore slopes downward.

Understand Meaning and Law of Demand

Demand is not just a wish to buy. It needs three things: desire for the good, money to pay for it, and willingness to spend that money. A wish without purchasing power is not demand. Demand is also always linked to a price and a period of time, such as ₹50 per kg per week.

A demand schedule is a table showing the quantity demanded at different prices. An individual demand schedule is for one buyer. A market demand schedule is the sum of all individual buyers' quantities at each price. When you plot the schedule with price on the vertical axis and quantity on the horizontal axis and join the points, you get the demand curve.

The law of demand says there is an inverse relationship between price and quantity demanded, assuming other things stay the same. This assumption is called ceteris paribus. It means income, tastes, prices of related goods and expectations do not change. If any of these changes, the law cannot be tested cleanly.

Why does the curve slope downward? There are standard reasons. First, the law of diminishing marginal utility: each extra unit gives less satisfaction, so you will buy more only at a lower price. Second, the income effect: when price falls, your real purchasing power rises, so you can buy more. Third, the substitution effect: when a good becomes cheaper than its substitutes, buyers switch to it. Fourth, new buyers enter at lower prices, and existing buyers find additional uses for the good.

There are exceptions where more is bought at a higher price. Examples are Giffen goods (very inferior goods like a basic staple for the poor), Veblen goods (prestige goods bought because they are costly), and cases where people expect prices to rise further. These are exceptions, not the rule.

Key rules to remember

Law of demand: Price ↑ ⇒ Quantity demanded ↓; Price ↓ ⇒ Quantity demanded ↑ (ceteris paribus); Inverse relationship. Always state the 'other things equal' condition.
Market demand: Market demand at a price = Σ individual demands at that price; Add quantities across buyers at the same price, not the prices.
Demand function: Dx = f(Px); Quantity demanded of good X depends on its own price, other factors held constant.
Assumptions of the law: Constant income, tastes, related goods' prices, expectations, number of buyers; Learn these as the 'ceteris paribus' list.

How to solve Meaning and Law of Demand questions

Use this method for theory questions and schedule-based questions on demand.

1Read the question and mark the command word: define, explain, state, illustrate or distinguish.
2Define demand using its three elements: desire, ability to pay, willingness to pay, tied to price and time.
3If a schedule is given, check that price falls as quantity rises. If it is asked for, build a table with price and quantity columns.
4State the law of demand with the inverse relationship and the ceteris paribus condition.
5Draw a neat diagram: price on the Y-axis, quantity on the X-axis, a downward sloping line labelled DD, with axes labelled.
6Give the reasons for the downward slope in separate points: diminishing marginal utility, income effect, substitution effect, new buyers, multiple uses.
7Add the exceptions (Giffen, Veblen, expectations) if the question says 'explain fully' or carries more marks.
8Close with a one-line conclusion linking price change to movement along the curve.

Quickest way: Four-line answer frame

When to use it: Use when time is short or the question carries few marks.

Line 1: Define demand in one sentence with price and time.
Line 2: State the law: price up, quantity down, other things equal.
Line 3: Draw a small DD curve with labelled axes.
Line 4: Give two reasons: income effect and substitution effect, plus diminishing marginal utility if space allows.

Common mistakes in Meaning and Law of Demand

Defining demand as only the desire to buy.
The everyday meaning of demand is 'want'.
Fix: Always include ability to pay and willingness to pay, and mention price and time period.
Leaving out 'other things remaining equal' in the law.
Students memorise only 'price up, demand down'.
Fix: End the law with ceteris paribus and list income, tastes and related prices as constant.
Drawing the curve with axes swapped or unlabelled.
Confusion with mathematics graphs where the cause goes on the X-axis.
Fix: In economics demand diagrams, put price on the Y-axis and quantity on the X-axis, and label DD, P and Q.
Treating Giffen goods as proof that the law is wrong.
Exceptions are read as rejections.
Fix: Say the law holds for normal cases and list Giffen goods, Veblen goods and price-rise expectations as exceptions.
Adding prices instead of quantities in a market demand schedule.
Rushing through the table.
Fix: Keep the price row fixed and add only the quantities of all buyers at that price.

Worked examples

Example 1

Two consumers, A and B, have these demands for tea packets per month. At ₹100: A buys 2, B buys 3. At ₹80: A buys 3, B buys 5. At ₹60: A buys 5, B buys 7. Prepare the market demand schedule and state what it shows.

Show the solution

Fix each price and add the quantities of A and B.
At ₹100: 2 + 3 = 5 packets.
At ₹80: 3 + 5 = 8 packets.
At ₹60: 5 + 7 = 12 packets.
Check the pattern: as price falls from ₹100 to ₹60, market quantity rises from 5 to 12.

Answer: Market demand is 5, 8 and 12 packets at ₹100, ₹80 and ₹60. Price and quantity move in opposite directions, so the schedule follows the law of demand.

Example 2

Explain why the demand curve slopes downward.

Show the solution

Define the curve: it shows quantity demanded at each price and slopes downward from left to right, reflecting the inverse relationship in the law of demand.
Diminishing marginal utility: each extra unit gives less satisfaction, so a buyer will pay less for it. More is bought only if price falls.
Income effect: a fall in price raises real income, so the buyer can purchase more of the good.
Substitution effect: when the good becomes cheaper relative to substitutes, buyers switch to it.
New buyers and more uses: a lower price brings in buyers who could not afford it earlier and allows use of the good in more ways.
Conclude: these forces together make quantity demanded rise as price falls, giving a downward sloping curve.

Answer: The curve slopes downward because of diminishing marginal utility, the income effect, the substitution effect, and the entry of new buyers and additional uses at lower prices.

Exam tips

Write the definition of demand with all three elements; examiners look for ability to pay and willingness to pay.
Always draw the DD curve with labelled axes. A neat diagram often earns separate marks.
In schedule questions, show the addition for each price row so partial marks are safe.
Keep the reasons for the downward slope as separate numbered points, not one long paragraph.
Do not confuse a movement along the curve (price change) with a shift of the curve; that belongs to determinants of demand.

Practice questions from Basics of Demand and Supply and Forms of Market Competition

Meaning and Law of Demand in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Meaning and Law of Demand: frequently asked questions

What is the law of demand in simple words?

It says that when the price of a good falls, people buy more of it, and when the price rises, they buy less, provided other factors stay the same. The relationship between price and quantity demanded is inverse.

Why does the demand curve slope downward?

The main reasons are diminishing marginal utility, the income effect and the substitution effect. Lower prices also bring in new buyers and create additional uses for the good.

What is a demand schedule?

It is a table that lists the quantity of a good demanded at different prices during a given time. A market demand schedule adds up the quantities of all buyers at each price.

What are the exceptions to the law of demand?

Common exceptions are Giffen goods, Veblen or prestige goods, and situations where buyers expect prices to rise further. In these cases quantity demanded may rise with price.