The demand for a commodity refers to the quantity of that commodity that consumers are willing and able to buy at a given price during a specific time period.

Option 1, "Desire for that commodity," is not the correct answer. Although desire may influence demand, it does not fully capture the concept of demand. Demand is more than just a desire; it also involves the willingness and ability to purchase the commodity.

Option 2, "Need for that commodity," is not the correct answer either. Need may influence demand, but it does not capture the concept completely. Demand is not solely based on need; it also depends on consumers` preferences, tastes, and other factors.

Option 3, "Quantity demanded of that commodity," is not the correct answer. While it is true that demand is related to the quantity demanded, it does not encompass the entire concept. Demand is not just about the quantity; it also includes the price and time period.

The correct answer is option 4, "Quantity demanded at a certain price during any particular period of time." This option accurately describes the concept of demand, which considers both the quantity of the commodity and the price at which it is demanded, within a specific time frame.