Bertrand's paradox

(probability) A problem within the classical interpretation of probability theory, illustrating how the principle of indifference may not produce definite, well-defined results for probabilities if it is applied uncritically when the domain of possibilities is infinite.

(economics) A hypothetical phenomenon where if the number of firms producing a product goes from one to two or more selling identical products with identical manufacturing costs, the price would be expected to decrease from the high price which one monopolistic firm would charge to a competitive at-cost price, if consumers choose which product to buy based solely on price and the firms try to undercut each other.