Money to serve well a variety of uses must be of different denominations, and "small change" is necessary to make small purchases and for exact settlement in larger payments that are not multiples of the standard unit.

The amount required (or most convenient to use) in each denomination of fractional coins is thus a more or less certain portion of each person's monetary demand, shaped by experience and fixed by habit.

For example, within certain elastic limits of convenience quarters may be used for halves, and dimes for nickels (and _vice versa_); but each person has a point of preference.

The total demand for each kind of change is the sum of the individual demands.

This point where the amount of coins of any denomination (in relation to the whole monetary system) is most convenient may be called the saturation point of that kind of small change, up to which point the people prefer a share of their money in that form, and beyond which they will, if free to choose, exchange that kind for other denominations (smaller or larger).