The study of expressing the effectiveness of an action in the modern Ossetian language shows that Ossetian prefixal verbs can denote not only the effectiveness of an action, but also various aspectualactional shades of effectiveness, which are denoted by verbs of special effective Aktionsarten. Similarity in terms of aspectual-actional meaning is observed in the verbs of the following Ossetian and Russian special effective Aktionsarten derived from telic verbs: distributive-total, cumulative, total, and softening. In the above semantics in both languages, verbs of the following Aktionsarten derived from atelic verbs coincide: inchoative, durative-limited, restrictive, semelfactive, and reiterative. A separate group of special effective Aktionsarten that distinguish Ossetian from Russian is formed by verbs with specific shades of effective actionality: partially effective, total-qualitative, instantaneously effective, thoroughly effective, intensively effective, normatively effective, and comparatively effective. A subject of particular attention in this article are the verbs with the fæprefix. An attempt is made to explain the reasons for the unlimited aspectual-actional activity of this prefix. According to the author, such activity is associated with the freedom of this prefix from the spatial-orientational semantics, which resulted in a later (than other prefixes) involvement in denoting the specific-process meaning of the imperfective aspect, or rather, the perceptivity of an action and, accordingly, other aspectual meanings. As a consequence, this prefix was in great aspectual-actional demand at the later stages of development of the aspect as a grammatical category in the Ossetian language. A comparison of functional and translational Ossetian and Russian aspectual-actional equivalents reveals both universal and idioethnic elements in assessing the nature of the progression and distribution of an action in time. Differences in this assessment (with similar perception by speakers of different languages of the same situations of extralinguistic reality) are of undoubted interest for Ossetian and Russian general and comparative aspectology.