Marginal

Marginal is an adjective used to describe something related to a margin or border, or something that lies at the edge of a defined scope. It can also describe an incremental or additional amount beyond a baseline, as in marginal changes or marginal costs. In common usage, marginal can imply limited importance or relevance, but in technical contexts it denotes a specific, measurable boundary or increment.

In economics, marginal concepts analyze the effects of small changes. Marginal cost is the increase in total cost from producing one additional unit of output. Marginal revenue is the additional income from selling that unit. Marginal utility is the extra satisfaction gained from consuming one more unit. Marginal analysis compares the benefit of a small change to its cost, often leading to profit-maximizing decisions. The marginal product of an input measures the change in output from a unit change in input, holding other inputs constant.

Marginal distribution or marginal probability describes the distribution of a single variable within a joint distribution, obtained by summing or integrating over the other variables. It contrasts with conditional distribution, which depends on the values of other variables.

Marginal tax rate is the percentage applied to the next dollar of income, used to describe the rate structure in progressive tax systems. It differs from the average tax rate, which is the total tax paid divided by total income, and from the effective rate, which accounts for deductions and credits.

Marginalia are notes, comments, or illustrations written in the margins of a text, historically significant for scholarly study and reception.

As a general term, marginal emphasizes edge, boundary, or incremental change across disciplines.