"U and Non-U: An essay on sociological linguistics" is the title of a 1954 article by Alan S. C. Ross in Neuphilologische Mitteilungen that identified various markers of upper-class ("U") and non-upper-class ("non-U") status in British English. The terms U and non-U, and the pastime of identifying expressions as belonging to one category or the other, were popularized by Nancy Mitford's book Noblesse Oblige: An Enquiry into the Identifiable Characteristics of the English Aristocracy, a collection that included Ross's essay and other writings on the topic.
Dialect differences are constantly changing, especially ones that are correlated with social class. One constant, or rather one constant source of change, is the fact that people who belong to a lower class generally want to sound as if they belong to a higher one. In particular, the middle class would like to sound like the upper class. At the same time, the upper class would like to sound cool, and one way of doing this is to borrow expressions from the lower class, because this makes one sound as if one doesn't care whether one sounds as if one belongs to the upper class. The resulting flow of vocabulary resembles a convection oven.
With this in mind, it is perhaps not so surprising that the expressions Ross and Mitford identified as non-U tend to sound more euphemistic or pretentious than their U counterparts. In many cases, though, the distinction sounds just as arbitrary as it is. Some examples:
- non-U: dentures
U: false teeth
- non-U: perfume
U: scent
- non-U: cycle
U: bike
- non-U: wealthy
U: rich
- non-U: preserve
U: jam
- non-U: home
U: house
- non-U: serviette
U: (table) napkin
- non-U: notepaper
U: writing-paper
- non-U: radio
U: wireless