Children as young as two use sentence structure to learn the meanings of verbs. We probed the generality of sensitivity to sentence structure by moving to a different semantic and syntactic domain, spatial prepositions. Twenty-six-month-olds used sentence structure to determine whether a new word was an object-category name ("This is a corp!") or a spatial-relational term ("This is acorp my box!"). We argue that children rely on the intimate relationship between nouns in sentences and semantic arguments of predicate terms: Noting that a new word takes noun arguments identifies the new word as a predicate term, and directs the child's attention to relations among its arguments.