This paper discusses the syntactic and semantic properties underlying root infinitival constructions as found in English and Spanish adult registers, which are here referred to as adult root infinitives (ARIs). It is shown, drawing from and extending earlier work, that ARIs consist of two overtly expressed parts: the root infinitive (RI) itself as some sort of exclamative and a Coda. Connectivity effects suggest that syntactically, RI and Coda form one structure. The semantics assumed here follows much work on tripartite focus structures and explores Portner and Zanuttini's (2003) widening operator R for exclamatives. As a whole, ARIs are analyzed as consisting of an exclamative operator (the syntactic counterpart of R), the RI (an indefinite descriptions of events that functions as its restrictor), and the Coda (the operator's main predicate).