Definiteness depends on crosslinguistic semantic variables, including count/mass distinction, which correlates with cognitive individuation of discrete entities and attention to shape rather than substance. Count/mass distinction is represented by definiteness markers in English but not in Levantine Arabic (LA). Replicating experiments by Liu and Gleason, Middleton, and Lucy and Gaskins, this study tested grammar of definiteness, cognitive individuation, and attention to shape vs. substance in LA heritage speakers of English (LAHSEs, aged 18‑25). The results show that LA definiteness parameters affect LAHSEs’ cognition but not their grammar of definiteness.