In addition, any word — this again applied in principle to every word in the language — could be negative by adding the affix un-, or could be strengthened by the affix plus-, or, for still greater emphasis doubleplus-. Thus, for example, uncold meant “warm” while pluscold and doublepluscold meant, respectively, “very cold” and “superlatively cold”. It was also possible, as in present-day English, to modify the meaning of almost any word by prepositional affixes such as ante-, post-, up-, down-, etc. By such methods it was possible to bring about an enormous diminution of vocabulary. Given, for instance, the word good, there was no need for such a word as bad, since the required meaning was equally well —indeed better— expressed by ungood. All that was necessary, in any case where two words formed a natural pair of opposites, was to decide which of them to suppress. Dark, for example, could be replaced by Unlight, or light by undark, according to preference.
1984 (by George Orwell): Excerpt from Appendix, “The Principles of Newspeak”