The article is devoted to peripheral language units: (1) to parenthetical words and expressions and (2) to response units (communicatives). These language units act as pragmatic markers in discourse; they reproduce the speaker's attitude to what (s) he is saying at the moment. Parenthetical words and communicatives are often treated as special discursive words and as gambits in discourse analysis: markers of a speech act these units are attached to for a more smooth flow of communication. These units have very poor grammar, they are idiomatically fixed and can hardly be analyzed by means of traditional linguistic devices. One can find out the meaning and usage features of parenthetical words and communicatives by looking at the way these units function in discourse and by analyzing the communicative tasks they fulfill. The first part of the article is devoted to the syntactic, semantic and pragmatic characteristics of parenthetical words. It is noted that the many parenthetical words specify and intensify a speech act. The addresser includes such units in her/his speech to make it more fluent, to make the addressee ready to perceive the coming speech act, or to intensify the speech act effect. Communicatives are words and word combinations used in dialog as response units. They are used to express agreement, disagreement, to answer etiquette formulas, to express different emotions and so on. In many linguistic works communicatives and parenthetical words are treated as one functional class. The words (and collocations) analyzed in the article can be used in discourse in both functions. Yet it is demonstrated that the functions and meaning of these groups of words are fundamentally different, and it is the reason to divide these groups and study them separately. Parenthetical words are only an optional supplement to speech act, while communicatives ARE speech acts, interaction moves in dialog. Opposite to parenthetical words, communicatives have phrase stress; being communicative reaction these units are accompanied with emotional mimics and gestures in oral dialog. All this information is very important for the description of communicatives. Some words used in both functions differ greatly in their meanings. For example, such synonymic collocations as bud' tak dobr, bud' tak liubezen, sdelay milost' [be so kind] as parenthetical words are used before or next to the directive to make it more delicate and polite; as a communicative unit these collocations fulfill the role of a thankful and a bit old-fashioned agreement, after the speaker gets a courteous offer to help him/her to do something useful to him/her or to somebody else.
