This groundbreaking book unveils the crucial role of network science in understanding the lexical organization of second languages via its exploration of English learners. Network science has become increasingly popular in the cognitive sciences, including linguistics. Phonological Networks and Their Growth in Second Languages is the first to explore lexical networks in learners of English as a second language with a focus on the relationships between phonological word forms in the mental lexicon. It highlights the contributions that network science can make to the study of lexical organization of second languages. Within the theoretical framework of evolving networks, lexical learning is seen as a process of network growth. The book models the lexicon as a growing phonological network that increases in size as language users advance through second language proficiency stages. As such, the analysis of specific growth algorithms (such as preferential attachment) accounts for observed mechanisms of lexical acquisition. Empirical models of evolving lexical networks can help shed light on the structural changes occurring as the second language lexicon expands.