Primary interjections consist of a group of prototypical units, which are associated with reflex cries by their origin, have an oral form called a vocal gesture, and written, conventional ones, with national characteristics. Analysis of similar features in pronunciation, spelling and semantics of prototypical units and linguistic differences of other units reveals universal characteristics of a limited number of prototypical interjections and linguistic specifity of the majority of primary interjections. Examples drawn from English, Russian and Kazakh languages demonstrate the ability of primary interjections to express the ambivalence of feelings and emotions. The article focuses on distinguishing instinctive and discursive categories of primary interjections concentrating on the mode of their production and purpose of use. The first category includes addressless exclamations that express a reaction to what is happening, as well as relevant feelings and emotions. The second group includes units that are explicitly or implicitly intended for the addressee of speech, which are used for communicative purposes. In contrast to instinctive interjections expressing spontaneous feelings and reactions, discursive units may reflect unreal emotions that the interlocutor expects to be demonstrated. In a pragmatic aspect, the use of primary interjections is considered to convey an ironic attitude to the subject of speech. The article provides an overview of language units that formally resemble primary interjections and make their identification difficult.