This paper explores the Russian adversative conjunction an ‘but, in fact.’ We describe typical contexts of its usage and single out semantic components that an introduces. In contemporary Russian an is used rarely, mainly as part of the word combination an net ‘but, in fact, not’ in rather similar contexts, and almost every time it can be substituted with no ‘but’ to which it seems to ascend etymologically. However, an cannot be used instead of no in every case: the spectrum of contexts where an is suitable is rather narrow in comparison with no contexts. So, an is relevant only in cases of an abnormal combination of situations but not in contradictory characterization. In addition, an does not necessarily mean the metaphysical abnormality (which is frequent with no usage), but rather deals with certain expectancy violations. Thus, it is better to say Dumali, pomret, an vykarabkalsya ‘We thought he would die, but he surprisingly came through’ than ? On zabolel, an vyzdorovel ‘He got ill, but recovered;’ in the second example it would be natural to use no. An marks the contrast between the initial reading of the situation and the way one sees it at the moment of speaking: Snachala kazalos', chto delo sovsem ploхo, an nichego, v konce koncov vyputalis' ‘At first, it seemed that things were going really badly, but it turned out to be ok, and in the end we pulled through.’ At the same time, it is absolutely impossible to say: *V konce koncov oni vyputalis', an snachala kazalos', chto delo sovsem ploхo ‘In the end they pulled through, but at first it seemed that things were going really badly.’ The inherent element of the majority of an contexts is dramatization. An releases a particular discourse positioning — utterances with an are produced from the position of superiority: the speaker feels his advantage over the hearer or other participants of the situation because he is the one who knew the true state of affairs before others.