WHEN IS A WORD A WORD

Although adult-based words co-occur in the period of transition to spe ech with a variety of non-word vocalizations, little attention has bee n given to the formidable problem of identifying these earliest words. This paper specifies explicit, maximally 'inclusive' identification p rocedures, with criteria based on both phonetic and contextual paramet ers. A formal system for evaluating phonetic match is suggested, as we ll as a set of child-derived functional categories reflecting use in c ontext. Analysis of word use across two samples of Io children each, f ollowed from 0;9 to 1;4, provides evidence to suggest that context-bou nd words can be 'trained' by focusing on eliciting language, but that the timing of context-flexible word use remains independent of such tr aining.