Choice Theory

Marginal Utility

The extra utility, or satisfaction, that a consumer receives from one additional unit of a specific product or service. (Marshal)

Indifference Theory (Replaced the marginal utility theory)

Suggests that utility is ordinarily measurable, rather than cardinally measurable; the consumer is assumed to be able to order or rank on scale  preferences all alternative sets of consumption possibilities (rather than to be required to assign numbers known as "utils" to measure utility). (Hicks and Allen)

Product Character Traits

The theory that states people don't buy products; they buy the characteristics of a product (Lancaster)

Family Household Theory

When attempting to change behavior of consumers, it's important to consider the family unit rather than the individual (Becker)

Time Management

When attempting to modify consumer behavior, the most important factor is how time is spent by each member of the household. (Peskin)