The best known artificial language is Esperanto. However, hundreds of other artificial languages have been proposed, although some have not progressed beyond the stage of sketches and few have seen much actual use. Those which are not consciously based on natural languages are called a priori languages. Such languages have been less successful than artificial languages built with elements of natural languages, such as Esperanto and Interlingua.However, a priori languages are of considerable theoretical interest, in particular from the point of view of language universals: if a universal property holds even of languages created "from scratch", then it can indeed be seen as a property of any (usable) human language. Therefore, in the description of the grammars of several a priori languages, particular attention will be given to whether their features are in accord with proposed universals, of both theGreenbergian and Chomskyan types.After an introduction one chapter each will be devoted to phonetics/phonology, writing systems, lexicon, morphology, syntax, and semantics. The languages described include aUI, Babm, Fitusa,Loglan/Lojban, and Suma. Most of these languages have received very little attention, even from scholars studying