In economics, marginal concepts are associated with a specific change in the quantity used of a good or service, as opposed to some notion of the over-all significance of that class of good or service, or of some total quantity thereof.
[1] The location of the margin for any individual corresponds to his or her endowment, broadly conceived to include opportunities.
This endowment is determined by many things including physical laws (which constrain how forms of energy and matter may be transformed), accidents of nature (which determine the presence of natural resources), and the outcomes of past decisions made both by others and by the individual himself or herself.
[2] For reasons of tractability, it is often assumed in neoclassical analysis that goods and services are continuously divisible.
[2] The marginal utility of a good or service is the utility of the specific use to which an agent would put a given increase in that good or service, or of the specific use that would be abandoned in response to a given decrease.