7. Project Summary/Abstract Spanish learners in the United States (US) are the fastest growing group among children, yet the research base to support their early oral language development in the face of language delay is lacking. To meet this identified research gap, the proposed overall objectives are to examine the specific influence of (a) dual- language learning (DLL) status and (b) caregiver input and interactions lexical-semantic development in children with language delay. Thus, the proposed study seeks to provide a detailed and longitudinal model of lexical-semantic growth in Spanish-learning children in the US who have early language delays and are at risk for language impairment. The central hypothesis is that a multidimensional and precise approach to the assessment of lexical-semantic growth that incorporates DLL status and language delay will be a better model and predictor of later language production than is the widely used single measure of vocabulary size. Further, it is hypothesized that high quality and quantity caregiver language input will predict stronger child outcomes across all multidimensional measures of lexical-semantic growth. Aim 1 takes a multidimensional approach by seeking to document the predictive validity of lexical-semantic breadth, access, and organization on vocabulary acquisition over time in Spanish learners with language delays. Aim 2 investigates the influence of dual- language exposure on lexical-semantic development. Aim 3 assesses the role of caregiver language input and interactions in supporting lexical-semantic growth and ultimately language outcomes. To meet these aims, Spanish-learning Latino children and their caregivers will be studied longitudinally across a well-known period of rapid lexical acquisition in toddlerhood. Lexical-semantic development will be assessed using novel behavioral tasks designed to capture the dynamic interaction between several dimensions (i.e., lexical- semantic breadth, organization, and access) that together support word learning. This approach represents a significant and meaningful contribution to the field because it meets a critical need to describe the specific deficits in lexical-semantic growth for children with LD with dual-language exposure. Importantly, the study examines the mechanism by which caregiver language input supports lexical-semantic growth in predicting later oral language outcomes in Latino Spanish-learning toddlers with early delays. The proposed work is innovative because it represents an interdisciplinary and substantive departure from the status quo by (a) providing a multidimensional understanding of lexical-semantic growth in children with LD, (b) examining Spanish learners in the US along a continuum of dual-language exposure, and (c) studying the caregiver input factors that promote lexical-semantic acquisition.