Lexicographic preferences
Ranking options by one all-important attribute first, breaking ties only by the next.
What it means
Lexicographic preferences describe a way of ranking options in which one attribute is treated as overwhelmingly dominant: alternatives are ordered entirely by that first attribute, and a second attribute is consulted only to break ties among options that are equal on the first, and so on down a strict priority list—exactly as words are ordered in a dictionary. Their defining feature is the refusal to trade off: no amount of a lower-priority attribute can ever compensate for any deficit on a higher-priority one, which violates the smooth substitutability assumed by standard indifference-curve analysis and means such preferences cannot be represented by a conventional utility function. They model decision rules where some consideration is non-negotiable, and they correspond closely to the 'take-the-best' and elimination-by-aspects heuristics, in which people decide by the most important cue and ignore the rest. As a description of real choice they capture protected values and attribute-by-attribute decision-making, though pure non-compensation is rare and often softened in practice. It matters because it marks the boundary of the standard trade-off model and links formal economics to how people actually simplify multi-attribute decisions.
Examples
A buyer who will only ever consider the cheapest car, and looks at color or brand solely to choose among equally cheap options, is using lexicographic preferences.
A flat-hunter who will consider nothing beyond a ten-minute walk from the school compares rent and garden size only among the flats that already pass that test.
A parent with a severely nut-allergic child screens menus for nut safety alone; taste, price and reviews decide only between restaurants that are already safe.