Perfectly inelastic demand means the demand curve is a vertical line (quantity demanded does not change with price). If supply increases (supply curve shifts right), the intersection point moves down along the vertical demand line, resulting in a lower price but the exact same quantity.

For a Giffen good (e.g., staple food like bread/rice for the very poor), the income effect of a price rise is so strong (consumers feel poorer and cut back on expensive foods like meat) that they end up buying MORE of the staple Giffen good, despite the price rise.

A change in the price of the good causes movement *along* the curve. A change in non-price determinants (Income, Tastes, Price of substitutes) shifts the entire curve left or right.

Positive cross elasticity means if the price of Good A rises, the demand for Good B rises. This happens with substitutes (people switch from expensive Tea to cheaper Coffee). For complements, it is negative.

A negative cross elasticity means that if the price of X rises, the demand for Y falls. This happens with complementary goods because they are consumed together (e.g., if the price of Petrol rises, demand for Cars may fall).

If a consumer is willing to pay ?100 for a product but buys it for ?80, the Consumer Surplus is ?20. It represents the net benefit to consumers.

An increase in demand shifts the demand curve to the right. With a fixed upward-sloping supply curve, this leads to a higher equilibrium price and a higher equilibrium quantity.

Veblen goods are luxury goods for which demand increases as price increases, because the higher price confers status (Conspicuous Consumption). This is an exception to the Law of Demand.

Movement along the supply curve (expansion or contraction) is caused ONLY by a change in the price of the good itself. All other factors shift the curve.

Unitary elasticity means the percentage change in quantity demanded is exactly equal to the percentage change in price.

When both demand and supply curves shift to the right by the same magnitude, the upward pressure on price from increased demand is exactly offset by the downward pressure on price from increased supply. However, both shifts contribute to an increase in the quantity traded, resulting in a higher equilibrium quantity at the same price.

A Price Ceiling sets a maximum legal price below the equilibrium price. At this lower price, quantity demanded increases (people want more cheap goods) while quantity supplied decreases (producers make less profit), resulting in excess demand or a shortage .

Perfect elasticity means that at a specific price, suppliers are willing to supply an infinite amount. Even a tiny drop in price reduces supply to zero. This is depicted by a horizontal line.

The Law of Demand states price and quantity are inversely related. Veblen goods (status symbols like diamonds) violate this because people buy MORE of them as their price rises to show off wealth.