all possible consumption combinations of goods that someone can afford, given the prices of goods, when all income is spent; the boundary of the opportunity set.

as we consume more of a good or service, the utility we get from additional units of the good or service tends to become smaller than what we received from earlier units

invisible hand Adam Smith's concept that individuals' self-interested behavior can lead to positive social outcomes.

when a country can produce a good at a lower cost in terms of other goods; or, when a country has a lower opportunity cost of production.

examination of decisions on the margin, meaning a little more or a little less from the status quo

opportunity cost measures cost by what we give up/forfeit in exchange; opportunity cost measures the value of the forgone alternative

opportunity set all possible combinations of consumption that someone can afford given the prices of goods and the individual’s income.