In economics, demand is the utility for a good or service of an economic agent, relative to his/her income. (Note: This distinguishes "demand" from "quantity demanded", where demand is a listing or graphing of quantity demanded at each possible price. In contrast to demand, quantity demanded is the exact quantity demanded at a certain price. Changing the actual price will change the quantity demanded, but it will not change the demand, because demand is a listing of quantities that would be bought at various prices, not just the actual price.)
Demand is a buyer's willingness and ability to pay a price for a specific quantity of a good or service. Demand refers to how much (quantity) of a product or service is desired by buyers at various prices. The quantity demanded is the amount of a product people are willing or able to buy at a certain price; the relationship between price and quantity demanded is known as the demand. (see also supply and demand). The term demand signifies the ability or the willingness to buy a particular commodity at a given point of time, ceteris paribus. Utility preferences and choices underlying demand can be represented as functions of cost, benefit, odds and other variables.
In the theory of Jacques Lacan, demand (French:demande) represents the way instinctive desires are inevitably alienated through the effects of language on the human condition. The concept of demand was developed by Lacan in parallel to those of need and desire to account for the role of speech on human aspirations. Demand forms part of Lacan's battle against the approach to language acquisition favored by ego psychology, and makes use of Kojeve's theory of desire. Demand is not a Freudian concept.
For Lacan, demand is the result of language acquisition on physical needs - the individual's wants are automatically filtered through the alien system of external signifiers.
Where traditionally psychoanalysis had recognised that learning to speak was a major step in the ego's acquisition of power over the world, and celebrated its capacity for increasing instinctual control, Lacan by contrast stressed the more sinister side of man's early submergence in language.