The aim of this paper is to describe and explain the role that linguistic interaction plays in category construction and communication, by looking at naturally occurring data of spoken language. First, it will be argued that there is a way of building categories that is inherently interactional and indexical, namely ad hoc categorization. Ad hoc categorization will be defined as a bottom-up exemplar driven process, that is dependent on context for both its construction and its interpretation, and crucially relies on non-exhaustivity and exemplification. After a brief overview of the linguistic strategies that may encode ad hoc categorization, we will concentrate on linguistic interaction, taking the perspective of so-called languaging. It will be shown that categorization is frequently instrumental to intersubjective aims, such mutual agreement, negotiation, and the general management of the speakers' positioning. In turn, it is collaboration between the interlocutors that allows to fine-tune categorization and achieve mutual understanding. Finally, we will focus on the incrementality of ad hoc categorization in interaction along two dimensions, namely, the identification of the category borders and the progressive anchoring of the category to the interlocutors' experience.