ABSTRACT In many of the world's languages grammatical aspect is used to indicate how events unfold over time. In English, activities that are ongoing can be distinguished from those that are completed using the morphological marker -ing. Using naturalistic observations of two children in their third year of life, we quantify the availability and reliability of the imperfective form in the ... [Show full abstract] communicative context of the child performing actions. On average, 30% of verbal descriptions refer to child actions that are grounded in the here-and-now. Of these utterances, there are two features of the communicative context that reliably map onto the functions of the imperfective, namely, that events are construed as ongoing and from within. The findings are discussed with reference to how the context in which a child hears aspectual language may limit the degrees of freedom on what these constructions mean.