Academic vocabulary networks were examined in 3 elementary grades textbook programs (first through fifth grade) in 3 domains--science, mathematics, and social studies. Within each program, a given network consisted of a focal domain-specific academic word and the collection of words from all grades that overlapped in meaning with the focal word. Academic words and the networks for each domain-specific academic word were computationally determined. For each network, the time at which the first network word appeared represented the inception of the network. The network's expansion across the grades was tracked as additional words appeared. The main research questions were as follows: (a) Did network growth patterns across grades vary according to domain? and, within domain, (b) Did network patterns vary according to two focal domain-specific academic word characteristics? The two focal word characteristics were the age at which the focal word's meaning was typically known and the timing of the introduction of the focal word. Multilevel growth model analyses were conducted. The dependent variable was number of words, called "nodes," in a network at each time point across the grades. Main conclusions were the following: (a) network patterns varied across domains, with social studies networks most different from those in the other two domains; and (b) network growth pattern varied according to selected focal word characteristics, and the focal word characteristic effect varied by domain.