_ Source: _Volume 53, Issue 2-4, pp 269 - 293 This article presents some results of the study of seventeen medieval treatises containing a logical analysis of the syncategorem ‘_an_’. On the one hand, a new classification is proposed of the literary genres of the _Logica Modernorum_, based on the four elements involved in the logical analysis of syncategorematic terms: the meaning of the syncategorem, logical rules, related sophisms, and proposed solutions. On the other, three texts are studied in detail, (...) showing the origins and development of the logical analysis of the syncategorem ‘_an_’ between the 12th and the 13th centuries. Finally, a comparative study is offered of different analyses of the sophism ‘_Tu scis an de mentiente sit falsum Sortem esse illum_’, a sophism that does not raise any problem as to the particle ‘_an_’, but introduces the issue of the truth conditions of the _dicta_. (shrink)