One of the two words economists use most, along with demand. These are the twin driving forces of the market economy. Supply is the amount of a good or service available at any particular price. The law of supply is that, other things remaining the same, the quantity supplied will increase as the price increases. The actual amount supplied will be determined, ultimately, by what the market price is, which depends on the amount demanded as well as what suppliers are willing to produce. What suppliers are willing to supply depends on several things:

• the cost of the factors of production;
• technology;
• the price of other goods and services (which, if high enough, might tempt the supplier to switch production to those products); and
• the ability of the supplier accurately to forecast demand and plan production to make the most of the opportunity.