Communication, whether in actual daily interactions or in academic educational institutions, needs to meet the condition of mutual understanding, follow-up, the intended message delivered, received and inferred by the interlocutors. In this academic work, the dyads of teachers and students are taken into account from the perspectives of Relevance Theory and Teacher Talk, thus integrating applied linguistics with pragmatics. The study has reached theoretical and practical conclusions: interaction in the classroom should achieve the principle of relevance, fulfilling teaching goals. Stimulus, as interaction initiation, is the first step, ostension is evidence of the speaker's intention and this can be stated explicitly and/or implicitly, depending on a dedicated inferential mechanism, local pragmatic modulation which leads to relevance-guided comprehension, i.e., the result the addressee arrives at. The dyads analyzed showed coherence as a basic concept for the utterances to achieve the principle of relevance; cohesion being a marginal property of the interactions. The dyads also showed the different categories of teacher talk, as put forward by the models adopted in the current study.